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postgres/src/backend/optimizer/prep/prepjointree.c
Tom Lane 1d98fdaed8 Avoid creating a RESULT RTE that's marked LATERAL. 
Commit 7266d0997 added code to pull up simple constant function
results, converting the RTE_FUNCTION RTE to a dummy RTE_RESULT
RTE since it no longer need be scanned.  But I forgot to clear
the LATERAL flag if the RTE has it set.  If the function reduced
to a constant, it surely contains no lateral references so this
simplification is logically OK.  It's needed because various other
places will Assert that RESULT RTEs aren't LATERAL.

Per bug #17097 from Yaoguang Chen.  Back-patch to v13 where the
faulty code came in.

Discussion: https://postgr.es/m/17097-3372ef9f798fc94f@postgresql.org
2021-07-09 13:38:24 -04:00

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/*-------------------------------------------------------------------------
*
* prepjointree.c
* Planner preprocessing for subqueries and join tree manipulation.
*
* NOTE: the intended sequence for invoking these operations is
* replace_empty_jointree
* pull_up_sublinks
* preprocess_function_rtes
* pull_up_subqueries
* flatten_simple_union_all
* do expression preprocessing (including flattening JOIN alias vars)
* reduce_outer_joins
* remove_useless_result_rtes
*
*
* Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/optimizer/prep/prepjointree.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "catalog/pg_type.h"
#include "funcapi.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/optimizer.h"
#include "optimizer/placeholder.h"
#include "optimizer/prep.h"
#include "optimizer/subselect.h"
#include "optimizer/tlist.h"
#include "parser/parse_relation.h"
#include "parser/parsetree.h"
#include "rewrite/rewriteManip.h"
typedef struct pullup_replace_vars_context
{
PlannerInfo *root;
List *targetlist; /* tlist of subquery being pulled up */
RangeTblEntry *target_rte; /* RTE of subquery */
Relids relids; /* relids within subquery, as numbered after
* pullup (set only if target_rte->lateral) */
bool *outer_hasSubLinks; /* -> outer query's hasSubLinks */
int varno; /* varno of subquery */
bool need_phvs; /* do we need PlaceHolderVars? */
bool wrap_non_vars; /* do we need 'em on *all* non-Vars? */
Node **rv_cache; /* cache for results with PHVs */
} pullup_replace_vars_context;
typedef struct reduce_outer_joins_state
{
Relids relids; /* base relids within this subtree */
bool contains_outer; /* does subtree contain outer join(s)? */
List *sub_states; /* List of states for subtree components */
} reduce_outer_joins_state;
static Node *pull_up_sublinks_jointree_recurse(PlannerInfo *root, Node *jtnode,
Relids *relids);
static Node *pull_up_sublinks_qual_recurse(PlannerInfo *root, Node *node,
Node **jtlink1, Relids available_rels1,
Node **jtlink2, Relids available_rels2);
static Node *pull_up_subqueries_recurse(PlannerInfo *root, Node *jtnode,
JoinExpr *lowest_outer_join,
JoinExpr *lowest_nulling_outer_join,
AppendRelInfo *containing_appendrel);
static Node *pull_up_simple_subquery(PlannerInfo *root, Node *jtnode,
RangeTblEntry *rte,
JoinExpr *lowest_outer_join,
JoinExpr *lowest_nulling_outer_join,
AppendRelInfo *containing_appendrel);
static Node *pull_up_simple_union_all(PlannerInfo *root, Node *jtnode,
RangeTblEntry *rte);
static void pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root,
int parentRTindex, Query *setOpQuery,
int childRToffset);
static void make_setop_translation_list(Query *query, Index newvarno,
AppendRelInfo *appinfo);
static bool is_simple_subquery(PlannerInfo *root, Query *subquery,
RangeTblEntry *rte,
JoinExpr *lowest_outer_join);
static Node *pull_up_simple_values(PlannerInfo *root, Node *jtnode,
RangeTblEntry *rte);
static bool is_simple_values(PlannerInfo *root, RangeTblEntry *rte);
static Node *pull_up_constant_function(PlannerInfo *root, Node *jtnode,
RangeTblEntry *rte,
JoinExpr *lowest_nulling_outer_join,
AppendRelInfo *containing_appendrel);
static bool is_simple_union_all(Query *subquery);
static bool is_simple_union_all_recurse(Node *setOp, Query *setOpQuery,
List *colTypes);
static bool is_safe_append_member(Query *subquery);
static bool jointree_contains_lateral_outer_refs(PlannerInfo *root,
Node *jtnode, bool restricted,
Relids safe_upper_varnos);
static void perform_pullup_replace_vars(PlannerInfo *root,
pullup_replace_vars_context *rvcontext,
JoinExpr *lowest_nulling_outer_join,
AppendRelInfo *containing_appendrel);
static void replace_vars_in_jointree(Node *jtnode,
pullup_replace_vars_context *context,
JoinExpr *lowest_nulling_outer_join);
static Node *pullup_replace_vars(Node *expr,
pullup_replace_vars_context *context);
static Node *pullup_replace_vars_callback(Var *var,
replace_rte_variables_context *context);
static Query *pullup_replace_vars_subquery(Query *query,
pullup_replace_vars_context *context);
static reduce_outer_joins_state *reduce_outer_joins_pass1(Node *jtnode);
static void reduce_outer_joins_pass2(Node *jtnode,
reduce_outer_joins_state *state,
PlannerInfo *root,
Relids nonnullable_rels,
List *nonnullable_vars,
List *forced_null_vars);
static Node *remove_useless_results_recurse(PlannerInfo *root, Node *jtnode);
static int get_result_relid(PlannerInfo *root, Node *jtnode);
static void remove_result_refs(PlannerInfo *root, int varno, Node *newjtloc);
static bool find_dependent_phvs(PlannerInfo *root, int varno);
static bool find_dependent_phvs_in_jointree(PlannerInfo *root,
Node *node, int varno);
static void substitute_phv_relids(Node *node,
int varno, Relids subrelids);
static void fix_append_rel_relids(List *append_rel_list, int varno,
Relids subrelids);
static Node *find_jointree_node_for_rel(Node *jtnode, int relid);
/*
* replace_empty_jointree
* If the Query's jointree is empty, replace it with a dummy RTE_RESULT
* relation.
*
* By doing this, we can avoid a bunch of corner cases that formerly existed
* for SELECTs with omitted FROM clauses. An example is that a subquery
* with empty jointree previously could not be pulled up, because that would
* have resulted in an empty relid set, making the subquery not uniquely
* identifiable for join or PlaceHolderVar processing.
*
* Unlike most other functions in this file, this function doesn't recurse;
* we rely on other processing to invoke it on sub-queries at suitable times.
*/
void
replace_empty_jointree(Query *parse)
{
RangeTblEntry *rte;
Index rti;
RangeTblRef *rtr;
/* Nothing to do if jointree is already nonempty */
if (parse->jointree->fromlist != NIL)
return;
/* We mustn't change it in the top level of a setop tree, either */
if (parse->setOperations)
return;
/* Create suitable RTE */
rte = makeNode(RangeTblEntry);
rte->rtekind = RTE_RESULT;
rte->eref = makeAlias("*RESULT*", NIL);
/* Add it to rangetable */
parse->rtable = lappend(parse->rtable, rte);
rti = list_length(parse->rtable);
/* And jam a reference into the jointree */
rtr = makeNode(RangeTblRef);
rtr->rtindex = rti;
parse->jointree->fromlist = list_make1(rtr);
}
/*
* pull_up_sublinks
* Attempt to pull up ANY and EXISTS SubLinks to be treated as
* semijoins or anti-semijoins.
*
* A clause "foo op ANY (sub-SELECT)" can be processed by pulling the
* sub-SELECT up to become a rangetable entry and treating the implied
* comparisons as quals of a semijoin. However, this optimization *only*
* works at the top level of WHERE or a JOIN/ON clause, because we cannot
* distinguish whether the ANY ought to return FALSE or NULL in cases
* involving NULL inputs. Also, in an outer join's ON clause we can only
* do this if the sublink is degenerate (ie, references only the nullable
* side of the join). In that case it is legal to push the semijoin
* down into the nullable side of the join. If the sublink references any
* nonnullable-side variables then it would have to be evaluated as part
* of the outer join, which makes things way too complicated.
*
* Under similar conditions, EXISTS and NOT EXISTS clauses can be handled
* by pulling up the sub-SELECT and creating a semijoin or anti-semijoin.
*
* This routine searches for such clauses and does the necessary parsetree
* transformations if any are found.
*
* This routine has to run before preprocess_expression(), so the quals
* clauses are not yet reduced to implicit-AND format, and are not guaranteed
* to be AND/OR-flat either. That means we need to recursively search through
* explicit AND clauses. We stop as soon as we hit a non-AND item.
*/
void
pull_up_sublinks(PlannerInfo *root)
{
Node *jtnode;
Relids relids;
/* Begin recursion through the jointree */
jtnode = pull_up_sublinks_jointree_recurse(root,
(Node *) root->parse->jointree,
&relids);
/*
* root->parse->jointree must always be a FromExpr, so insert a dummy one
* if we got a bare RangeTblRef or JoinExpr out of the recursion.
*/
if (IsA(jtnode, FromExpr))
root->parse->jointree = (FromExpr *) jtnode;
else
root->parse->jointree = makeFromExpr(list_make1(jtnode), NULL);
}
/*
* Recurse through jointree nodes for pull_up_sublinks()
*
* In addition to returning the possibly-modified jointree node, we return
* a relids set of the contained rels into *relids.
*/
static Node *
pull_up_sublinks_jointree_recurse(PlannerInfo *root, Node *jtnode,
Relids *relids)
{
if (jtnode == NULL)
{
*relids = NULL;
}
else if (IsA(jtnode, RangeTblRef))
{
int varno = ((RangeTblRef *) jtnode)->rtindex;
*relids = bms_make_singleton(varno);
/* jtnode is returned unmodified */
}
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
List *newfromlist = NIL;
Relids frelids = NULL;
FromExpr *newf;
Node *jtlink;
ListCell *l;
/* First, recurse to process children and collect their relids */
foreach(l, f->fromlist)
{
Node *newchild;
Relids childrelids;
newchild = pull_up_sublinks_jointree_recurse(root,
lfirst(l),
&childrelids);
newfromlist = lappend(newfromlist, newchild);
frelids = bms_join(frelids, childrelids);
}
/* Build the replacement FromExpr; no quals yet */
newf = makeFromExpr(newfromlist, NULL);
/* Set up a link representing the rebuilt jointree */
jtlink = (Node *) newf;
/* Now process qual --- all children are available for use */
newf->quals = pull_up_sublinks_qual_recurse(root, f->quals,
&jtlink, frelids,
NULL, NULL);
/*
* Note that the result will be either newf, or a stack of JoinExprs
* with newf at the base. We rely on subsequent optimization steps to
* flatten this and rearrange the joins as needed.
*
* Although we could include the pulled-up subqueries in the returned
* relids, there's no need since upper quals couldn't refer to their
* outputs anyway.
*/
*relids = frelids;
jtnode = jtlink;
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j;
Relids leftrelids;
Relids rightrelids;
Node *jtlink;
/*
* Make a modifiable copy of join node, but don't bother copying its
* subnodes (yet).
*/
j = (JoinExpr *) palloc(sizeof(JoinExpr));
memcpy(j, jtnode, sizeof(JoinExpr));
jtlink = (Node *) j;
/* Recurse to process children and collect their relids */
j->larg = pull_up_sublinks_jointree_recurse(root, j->larg,
&leftrelids);
j->rarg = pull_up_sublinks_jointree_recurse(root, j->rarg,
&rightrelids);
/*
* Now process qual, showing appropriate child relids as available,
* and attach any pulled-up jointree items at the right place. In the
* inner-join case we put new JoinExprs above the existing one (much
* as for a FromExpr-style join). In outer-join cases the new
* JoinExprs must go into the nullable side of the outer join. The
* point of the available_rels machinations is to ensure that we only
* pull up quals for which that's okay.
*
* We don't expect to see any pre-existing JOIN_SEMI or JOIN_ANTI
* nodes here.
*/
switch (j->jointype)
{
case JOIN_INNER:
j->quals = pull_up_sublinks_qual_recurse(root, j->quals,
&jtlink,
bms_union(leftrelids,
rightrelids),
NULL, NULL);
break;
case JOIN_LEFT:
j->quals = pull_up_sublinks_qual_recurse(root, j->quals,
&j->rarg,
rightrelids,
NULL, NULL);
break;
case JOIN_FULL:
/* can't do anything with full-join quals */
break;
case JOIN_RIGHT:
j->quals = pull_up_sublinks_qual_recurse(root, j->quals,
&j->larg,
leftrelids,
NULL, NULL);
break;
default:
elog(ERROR, "unrecognized join type: %d",
(int) j->jointype);
break;
}
/*
* Although we could include the pulled-up subqueries in the returned
* relids, there's no need since upper quals couldn't refer to their
* outputs anyway. But we *do* need to include the join's own rtindex
* because we haven't yet collapsed join alias variables, so upper
* levels would mistakenly think they couldn't use references to this
* join.
*/
*relids = bms_join(leftrelids, rightrelids);
if (j->rtindex)
*relids = bms_add_member(*relids, j->rtindex);
jtnode = jtlink;
}
else
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(jtnode));
return jtnode;
}
/*
* Recurse through top-level qual nodes for pull_up_sublinks()
*
* jtlink1 points to the link in the jointree where any new JoinExprs should
* be inserted if they reference available_rels1 (i.e., available_rels1
* denotes the relations present underneath jtlink1). Optionally, jtlink2 can
* point to a second link where new JoinExprs should be inserted if they
* reference available_rels2 (pass NULL for both those arguments if not used).
* Note that SubLinks referencing both sets of variables cannot be optimized.
* If we find multiple pull-up-able SubLinks, they'll get stacked onto jtlink1
* and/or jtlink2 in the order we encounter them. We rely on subsequent
* optimization to rearrange the stack if appropriate.
*
* Returns the replacement qual node, or NULL if the qual should be removed.
*/
static Node *
pull_up_sublinks_qual_recurse(PlannerInfo *root, Node *node,
Node **jtlink1, Relids available_rels1,
Node **jtlink2, Relids available_rels2)
{
if (node == NULL)
return NULL;
if (IsA(node, SubLink))
{
SubLink *sublink = (SubLink *) node;
JoinExpr *j;
Relids child_rels;
/* Is it a convertible ANY or EXISTS clause? */
if (sublink->subLinkType == ANY_SUBLINK)
{
if ((j = convert_ANY_sublink_to_join(root, sublink,
available_rels1)) != NULL)
{
/* Yes; insert the new join node into the join tree */
j->larg = *jtlink1;
*jtlink1 = (Node *) j;
/* Recursively process pulled-up jointree nodes */
j->rarg = pull_up_sublinks_jointree_recurse(root,
j->rarg,
&child_rels);
/*
* Now recursively process the pulled-up quals. Any inserted
* joins can get stacked onto either j->larg or j->rarg,
* depending on which rels they reference.
*/
j->quals = pull_up_sublinks_qual_recurse(root,
j->quals,
&j->larg,
available_rels1,
&j->rarg,
child_rels);
/* Return NULL representing constant TRUE */
return NULL;
}
if (available_rels2 != NULL &&
(j = convert_ANY_sublink_to_join(root, sublink,
available_rels2)) != NULL)
{
/* Yes; insert the new join node into the join tree */
j->larg = *jtlink2;
*jtlink2 = (Node *) j;
/* Recursively process pulled-up jointree nodes */
j->rarg = pull_up_sublinks_jointree_recurse(root,
j->rarg,
&child_rels);
/*
* Now recursively process the pulled-up quals. Any inserted
* joins can get stacked onto either j->larg or j->rarg,
* depending on which rels they reference.
*/
j->quals = pull_up_sublinks_qual_recurse(root,
j->quals,
&j->larg,
available_rels2,
&j->rarg,
child_rels);
/* Return NULL representing constant TRUE */
return NULL;
}
}
else if (sublink->subLinkType == EXISTS_SUBLINK)
{
if ((j = convert_EXISTS_sublink_to_join(root, sublink, false,
available_rels1)) != NULL)
{
/* Yes; insert the new join node into the join tree */
j->larg = *jtlink1;
*jtlink1 = (Node *) j;
/* Recursively process pulled-up jointree nodes */
j->rarg = pull_up_sublinks_jointree_recurse(root,
j->rarg,
&child_rels);
/*
* Now recursively process the pulled-up quals. Any inserted
* joins can get stacked onto either j->larg or j->rarg,
* depending on which rels they reference.
*/
j->quals = pull_up_sublinks_qual_recurse(root,
j->quals,
&j->larg,
available_rels1,
&j->rarg,
child_rels);
/* Return NULL representing constant TRUE */
return NULL;
}
if (available_rels2 != NULL &&
(j = convert_EXISTS_sublink_to_join(root, sublink, false,
available_rels2)) != NULL)
{
/* Yes; insert the new join node into the join tree */
j->larg = *jtlink2;
*jtlink2 = (Node *) j;
/* Recursively process pulled-up jointree nodes */
j->rarg = pull_up_sublinks_jointree_recurse(root,
j->rarg,
&child_rels);
/*
* Now recursively process the pulled-up quals. Any inserted
* joins can get stacked onto either j->larg or j->rarg,
* depending on which rels they reference.
*/
j->quals = pull_up_sublinks_qual_recurse(root,
j->quals,
&j->larg,
available_rels2,
&j->rarg,
child_rels);
/* Return NULL representing constant TRUE */
return NULL;
}
}
/* Else return it unmodified */
return node;
}
if (is_notclause(node))
{
/* If the immediate argument of NOT is EXISTS, try to convert */
SubLink *sublink = (SubLink *) get_notclausearg((Expr *) node);
JoinExpr *j;
Relids child_rels;
if (sublink && IsA(sublink, SubLink))
{
if (sublink->subLinkType == EXISTS_SUBLINK)
{
if ((j = convert_EXISTS_sublink_to_join(root, sublink, true,
available_rels1)) != NULL)
{
/* Yes; insert the new join node into the join tree */
j->larg = *jtlink1;
*jtlink1 = (Node *) j;
/* Recursively process pulled-up jointree nodes */
j->rarg = pull_up_sublinks_jointree_recurse(root,
j->rarg,
&child_rels);
/*
* Now recursively process the pulled-up quals. Because
* we are underneath a NOT, we can't pull up sublinks that
* reference the left-hand stuff, but it's still okay to
* pull up sublinks referencing j->rarg.
*/
j->quals = pull_up_sublinks_qual_recurse(root,
j->quals,
&j->rarg,
child_rels,
NULL, NULL);
/* Return NULL representing constant TRUE */
return NULL;
}
if (available_rels2 != NULL &&
(j = convert_EXISTS_sublink_to_join(root, sublink, true,
available_rels2)) != NULL)
{
/* Yes; insert the new join node into the join tree */
j->larg = *jtlink2;
*jtlink2 = (Node *) j;
/* Recursively process pulled-up jointree nodes */
j->rarg = pull_up_sublinks_jointree_recurse(root,
j->rarg,
&child_rels);
/*
* Now recursively process the pulled-up quals. Because
* we are underneath a NOT, we can't pull up sublinks that
* reference the left-hand stuff, but it's still okay to
* pull up sublinks referencing j->rarg.
*/
j->quals = pull_up_sublinks_qual_recurse(root,
j->quals,
&j->rarg,
child_rels,
NULL, NULL);
/* Return NULL representing constant TRUE */
return NULL;
}
}
}
/* Else return it unmodified */
return node;
}
if (is_andclause(node))
{
/* Recurse into AND clause */
List *newclauses = NIL;
ListCell *l;
foreach(l, ((BoolExpr *) node)->args)
{
Node *oldclause = (Node *) lfirst(l);
Node *newclause;
newclause = pull_up_sublinks_qual_recurse(root,
oldclause,
jtlink1,
available_rels1,
jtlink2,
available_rels2);
if (newclause)
newclauses = lappend(newclauses, newclause);
}
/* We might have got back fewer clauses than we started with */
if (newclauses == NIL)
return NULL;
else if (list_length(newclauses) == 1)
return (Node *) linitial(newclauses);
else
return (Node *) make_andclause(newclauses);
}
/* Stop if not an AND */
return node;
}
/*
* preprocess_function_rtes
* Constant-simplify any FUNCTION RTEs in the FROM clause, and then
* attempt to "inline" any that are set-returning functions.
*
* If an RTE_FUNCTION rtable entry invokes a set-returning function that
* contains just a simple SELECT, we can convert the rtable entry to an
* RTE_SUBQUERY entry exposing the SELECT directly. This is especially
* useful if the subquery can then be "pulled up" for further optimization,
* but we do it even if not, to reduce executor overhead.
*
* This has to be done before we have started to do any optimization of
* subqueries, else any such steps wouldn't get applied to subqueries
* obtained via inlining. However, we do it after pull_up_sublinks
* so that we can inline any functions used in SubLink subselects.
*
* The reason for applying const-simplification at this stage is that
* (a) we'd need to do it anyway to inline a SRF, and (b) by doing it now,
* we can be sure that pull_up_constant_function() will see constants
* if there are constants to be seen. This approach also guarantees
* that every FUNCTION RTE has been const-simplified, allowing planner.c's
* preprocess_expression() to skip doing it again.
*
* Like most of the planner, this feels free to scribble on its input data
* structure.
*/
void
preprocess_function_rtes(PlannerInfo *root)
{
ListCell *rt;
foreach(rt, root->parse->rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(rt);
if (rte->rtekind == RTE_FUNCTION)
{
Query *funcquery;
/* Apply const-simplification */
rte->functions = (List *)
eval_const_expressions(root, (Node *) rte->functions);
/* Check safety of expansion, and expand if possible */
funcquery = inline_set_returning_function(root, rte);
if (funcquery)
{
/* Successful expansion, convert the RTE to a subquery */
rte->rtekind = RTE_SUBQUERY;
rte->subquery = funcquery;
rte->security_barrier = false;
/* Clear fields that should not be set in a subquery RTE */
rte->functions = NIL;
rte->funcordinality = false;
}
}
}
}
/*
* pull_up_subqueries
* Look for subqueries in the rangetable that can be pulled up into
* the parent query. If the subquery has no special features like
* grouping/aggregation then we can merge it into the parent's jointree.
* Also, subqueries that are simple UNION ALL structures can be
* converted into "append relations".
*/
void
pull_up_subqueries(PlannerInfo *root)
{
/* Top level of jointree must always be a FromExpr */
Assert(IsA(root->parse->jointree, FromExpr));
/* Recursion starts with no containing join nor appendrel */
root->parse->jointree = (FromExpr *)
pull_up_subqueries_recurse(root, (Node *) root->parse->jointree,
NULL, NULL, NULL);
/* We should still have a FromExpr */
Assert(IsA(root->parse->jointree, FromExpr));
}
/*
* pull_up_subqueries_recurse
* Recursive guts of pull_up_subqueries.
*
* This recursively processes the jointree and returns a modified jointree.
*
* If this jointree node is within either side of an outer join, then
* lowest_outer_join references the lowest such JoinExpr node; otherwise
* it is NULL. We use this to constrain the effects of LATERAL subqueries.
*
* If this jointree node is within the nullable side of an outer join, then
* lowest_nulling_outer_join references the lowest such JoinExpr node;
* otherwise it is NULL. This forces use of the PlaceHolderVar mechanism for
* references to non-nullable targetlist items, but only for references above
* that join.
*
* If we are looking at a member subquery of an append relation,
* containing_appendrel describes that relation; else it is NULL.
* This forces use of the PlaceHolderVar mechanism for all non-Var targetlist
* items, and puts some additional restrictions on what can be pulled up.
*
* A tricky aspect of this code is that if we pull up a subquery we have
* to replace Vars that reference the subquery's outputs throughout the
* parent query, including quals attached to jointree nodes above the one
* we are currently processing! We handle this by being careful to maintain
* validity of the jointree structure while recursing, in the following sense:
* whenever we recurse, all qual expressions in the tree must be reachable
* from the top level, in case the recursive call needs to modify them.
*
* Notice also that we can't turn pullup_replace_vars loose on the whole
* jointree, because it'd return a mutated copy of the tree; we have to
* invoke it just on the quals, instead. This behavior is what makes it
* reasonable to pass lowest_outer_join and lowest_nulling_outer_join as
* pointers rather than some more-indirect way of identifying the lowest
* OJs. Likewise, we don't replace append_rel_list members but only their
* substructure, so the containing_appendrel reference is safe to use.
*/
static Node *
pull_up_subqueries_recurse(PlannerInfo *root, Node *jtnode,
JoinExpr *lowest_outer_join,
JoinExpr *lowest_nulling_outer_join,
AppendRelInfo *containing_appendrel)
{
Assert(jtnode != NULL);
if (IsA(jtnode, RangeTblRef))
{
int varno = ((RangeTblRef *) jtnode)->rtindex;
RangeTblEntry *rte = rt_fetch(varno, root->parse->rtable);
/*
* Is this a subquery RTE, and if so, is the subquery simple enough to
* pull up?
*
* If we are looking at an append-relation member, we can't pull it up
* unless is_safe_append_member says so.
*/
if (rte->rtekind == RTE_SUBQUERY &&
is_simple_subquery(root, rte->subquery, rte, lowest_outer_join) &&
(containing_appendrel == NULL ||
is_safe_append_member(rte->subquery)))
return pull_up_simple_subquery(root, jtnode, rte,
lowest_outer_join,
lowest_nulling_outer_join,
containing_appendrel);
/*
* Alternatively, is it a simple UNION ALL subquery? If so, flatten
* into an "append relation".
*
* It's safe to do this regardless of whether this query is itself an
* appendrel member. (If you're thinking we should try to flatten the
* two levels of appendrel together, you're right; but we handle that
* in set_append_rel_pathlist, not here.)
*/
if (rte->rtekind == RTE_SUBQUERY &&
is_simple_union_all(rte->subquery))
return pull_up_simple_union_all(root, jtnode, rte);
/*
* Or perhaps it's a simple VALUES RTE?
*
* We don't allow VALUES pullup below an outer join nor into an
* appendrel (such cases are impossible anyway at the moment).
*/
if (rte->rtekind == RTE_VALUES &&
lowest_outer_join == NULL &&
containing_appendrel == NULL &&
is_simple_values(root, rte))
return pull_up_simple_values(root, jtnode, rte);
/*
* Or perhaps it's a FUNCTION RTE that we could inline?
*/
if (rte->rtekind == RTE_FUNCTION)
return pull_up_constant_function(root, jtnode, rte,
lowest_nulling_outer_join,
containing_appendrel);
/* Otherwise, do nothing at this node. */
}
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
ListCell *l;
Assert(containing_appendrel == NULL);
/* Recursively transform all the child nodes */
foreach(l, f->fromlist)
{
lfirst(l) = pull_up_subqueries_recurse(root, lfirst(l),
lowest_outer_join,
lowest_nulling_outer_join,
NULL);
}
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
Assert(containing_appendrel == NULL);
/* Recurse, being careful to tell myself when inside outer join */
switch (j->jointype)
{
case JOIN_INNER:
j->larg = pull_up_subqueries_recurse(root, j->larg,
lowest_outer_join,
lowest_nulling_outer_join,
NULL);
j->rarg = pull_up_subqueries_recurse(root, j->rarg,
lowest_outer_join,
lowest_nulling_outer_join,
NULL);
break;
case JOIN_LEFT:
case JOIN_SEMI:
case JOIN_ANTI:
j->larg = pull_up_subqueries_recurse(root, j->larg,
j,
lowest_nulling_outer_join,
NULL);
j->rarg = pull_up_subqueries_recurse(root, j->rarg,
j,
j,
NULL);
break;
case JOIN_FULL:
j->larg = pull_up_subqueries_recurse(root, j->larg,
j,
j,
NULL);
j->rarg = pull_up_subqueries_recurse(root, j->rarg,
j,
j,
NULL);
break;
case JOIN_RIGHT:
j->larg = pull_up_subqueries_recurse(root, j->larg,
j,
j,
NULL);
j->rarg = pull_up_subqueries_recurse(root, j->rarg,
j,
lowest_nulling_outer_join,
NULL);
break;
default:
elog(ERROR, "unrecognized join type: %d",
(int) j->jointype);
break;
}
}
else
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(jtnode));
return jtnode;
}
/*
* pull_up_simple_subquery
* Attempt to pull up a single simple subquery.
*
* jtnode is a RangeTblRef that has been tentatively identified as a simple
* subquery by pull_up_subqueries. We return the replacement jointree node,
* or jtnode itself if we determine that the subquery can't be pulled up
* after all.
*
* rte is the RangeTblEntry referenced by jtnode. Remaining parameters are
* as for pull_up_subqueries_recurse.
*/
static Node *
pull_up_simple_subquery(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte,
JoinExpr *lowest_outer_join,
JoinExpr *lowest_nulling_outer_join,
AppendRelInfo *containing_appendrel)
{
Query *parse = root->parse;
int varno = ((RangeTblRef *) jtnode)->rtindex;
Query *subquery;
PlannerInfo *subroot;
int rtoffset;
pullup_replace_vars_context rvcontext;
ListCell *lc;
/*
* Need a modifiable copy of the subquery to hack on. Even if we didn't
* sometimes choose not to pull up below, we must do this to avoid
* problems if the same subquery is referenced from multiple jointree
* items (which can't happen normally, but might after rule rewriting).
*/
subquery = copyObject(rte->subquery);
/*
* Create a PlannerInfo data structure for this subquery.
*
* NOTE: the next few steps should match the first processing in
* subquery_planner(). Can we refactor to avoid code duplication, or
* would that just make things uglier?
*/
subroot = makeNode(PlannerInfo);
subroot->parse = subquery;
subroot->glob = root->glob;
subroot->query_level = root->query_level;
subroot->parent_root = root->parent_root;
subroot->plan_params = NIL;
subroot->outer_params = NULL;
subroot->planner_cxt = CurrentMemoryContext;
subroot->init_plans = NIL;
subroot->cte_plan_ids = NIL;
subroot->multiexpr_params = NIL;
subroot->eq_classes = NIL;
subroot->ec_merging_done = false;
subroot->all_result_relids = NULL;
subroot->leaf_result_relids = NULL;
subroot->append_rel_list = NIL;
subroot->row_identity_vars = NIL;
subroot->rowMarks = NIL;
memset(subroot->upper_rels, 0, sizeof(subroot->upper_rels));
memset(subroot->upper_targets, 0, sizeof(subroot->upper_targets));
subroot->processed_tlist = NIL;
subroot->update_colnos = NIL;
subroot->grouping_map = NULL;
subroot->minmax_aggs = NIL;
subroot->qual_security_level = 0;
subroot->hasRecursion = false;
subroot->wt_param_id = -1;
subroot->non_recursive_path = NULL;
/* No CTEs to worry about */
Assert(subquery->cteList == NIL);
/*
* If the FROM clause is empty, replace it with a dummy RTE_RESULT RTE, so
* that we don't need so many special cases to deal with that situation.
*/
replace_empty_jointree(subquery);
/*
* Pull up any SubLinks within the subquery's quals, so that we don't
* leave unoptimized SubLinks behind.
*/
if (subquery->hasSubLinks)
pull_up_sublinks(subroot);
/*
* Similarly, preprocess its function RTEs to inline any set-returning
* functions in its rangetable.
*/
preprocess_function_rtes(subroot);
/*
* Recursively pull up the subquery's subqueries, so that
* pull_up_subqueries' processing is complete for its jointree and
* rangetable.
*
* Note: it's okay that the subquery's recursion starts with NULL for
* containing-join info, even if we are within an outer join in the upper
* query; the lower query starts with a clean slate for outer-join
* semantics. Likewise, we needn't pass down appendrel state.
*/
pull_up_subqueries(subroot);
/*
* Now we must recheck whether the subquery is still simple enough to pull
* up. If not, abandon processing it.
*
* We don't really need to recheck all the conditions involved, but it's
* easier just to keep this "if" looking the same as the one in
* pull_up_subqueries_recurse.
*/
if (is_simple_subquery(root, subquery, rte, lowest_outer_join) &&
(containing_appendrel == NULL || is_safe_append_member(subquery)))
{
/* good to go */
}
else
{
/*
* Give up, return unmodified RangeTblRef.
*
* Note: The work we just did will be redone when the subquery gets
* planned on its own. Perhaps we could avoid that by storing the
* modified subquery back into the rangetable, but I'm not gonna risk
* it now.
*/
return jtnode;
}
/*
* We must flatten any join alias Vars in the subquery's targetlist,
* because pulling up the subquery's subqueries might have changed their
* expansions into arbitrary expressions, which could affect
* pullup_replace_vars' decisions about whether PlaceHolderVar wrappers
* are needed for tlist entries. (Likely it'd be better to do
* flatten_join_alias_vars on the whole query tree at some earlier stage,
* maybe even in the rewriter; but for now let's just fix this case here.)
*/
subquery->targetList = (List *)
flatten_join_alias_vars(subroot->parse, (Node *) subquery->targetList);
/*
* Adjust level-0 varnos in subquery so that we can append its rangetable
* to upper query's. We have to fix the subquery's append_rel_list as
* well.
*/
rtoffset = list_length(parse->rtable);
OffsetVarNodes((Node *) subquery, rtoffset, 0);
OffsetVarNodes((Node *) subroot->append_rel_list, rtoffset, 0);
/*
* Upper-level vars in subquery are now one level closer to their parent
* than before.
*/
IncrementVarSublevelsUp((Node *) subquery, -1, 1);
IncrementVarSublevelsUp((Node *) subroot->append_rel_list, -1, 1);
/*
* The subquery's targetlist items are now in the appropriate form to
* insert into the top query, except that we may need to wrap them in
* PlaceHolderVars. Set up required context data for pullup_replace_vars.
*/
rvcontext.root = root;
rvcontext.targetlist = subquery->targetList;
rvcontext.target_rte = rte;
if (rte->lateral)
rvcontext.relids = get_relids_in_jointree((Node *) subquery->jointree,
true);
else /* won't need relids */
rvcontext.relids = NULL;
rvcontext.outer_hasSubLinks = &parse->hasSubLinks;
rvcontext.varno = varno;
/* these flags will be set below, if needed */
rvcontext.need_phvs = false;
rvcontext.wrap_non_vars = false;
/* initialize cache array with indexes 0 .. length(tlist) */
rvcontext.rv_cache = palloc0((list_length(subquery->targetList) + 1) *
sizeof(Node *));
/*
* If we are under an outer join then non-nullable items and lateral
* references may have to be turned into PlaceHolderVars.
*/
if (lowest_nulling_outer_join != NULL)
rvcontext.need_phvs = true;
/*
* If we are dealing with an appendrel member then anything that's not a
* simple Var has to be turned into a PlaceHolderVar. We force this to
* ensure that what we pull up doesn't get merged into a surrounding
* expression during later processing and then fail to match the
* expression actually available from the appendrel.
*/
if (containing_appendrel != NULL)
{
rvcontext.need_phvs = true;
rvcontext.wrap_non_vars = true;
}
/*
* If the parent query uses grouping sets, we need a PlaceHolderVar for
* anything that's not a simple Var. Again, this ensures that expressions
* retain their separate identity so that they will match grouping set
* columns when appropriate. (It'd be sufficient to wrap values used in
* grouping set columns, and do so only in non-aggregated portions of the
* tlist and havingQual, but that would require a lot of infrastructure
* that pullup_replace_vars hasn't currently got.)
*/
if (parse->groupingSets)
{
rvcontext.need_phvs = true;
rvcontext.wrap_non_vars = true;
}
/*
* Replace all of the top query's references to the subquery's outputs
* with copies of the adjusted subtlist items, being careful not to
* replace any of the jointree structure.
*/
perform_pullup_replace_vars(root, &rvcontext,
lowest_nulling_outer_join,
containing_appendrel);
/*
* If the subquery had a LATERAL marker, propagate that to any of its
* child RTEs that could possibly now contain lateral cross-references.
* The children might or might not contain any actual lateral
* cross-references, but we have to mark the pulled-up child RTEs so that
* later planner stages will check for such.
*/
if (rte->lateral)
{
foreach(lc, subquery->rtable)
{
RangeTblEntry *child_rte = (RangeTblEntry *) lfirst(lc);
switch (child_rte->rtekind)
{
case RTE_RELATION:
if (child_rte->tablesample)
child_rte->lateral = true;
break;
case RTE_SUBQUERY:
case RTE_FUNCTION:
case RTE_VALUES:
case RTE_TABLEFUNC:
child_rte->lateral = true;
break;
case RTE_JOIN:
case RTE_CTE:
case RTE_NAMEDTUPLESTORE:
case RTE_RESULT:
/* these can't contain any lateral references */
break;
}
}
}
/*
* Now append the adjusted rtable entries to upper query. (We hold off
* until after fixing the upper rtable entries; no point in running that
* code on the subquery ones too.)
*/
parse->rtable = list_concat(parse->rtable, subquery->rtable);
/*
* Pull up any FOR UPDATE/SHARE markers, too. (OffsetVarNodes already
* adjusted the marker rtindexes, so just concat the lists.)
*/
parse->rowMarks = list_concat(parse->rowMarks, subquery->rowMarks);
/*
* We also have to fix the relid sets of any PlaceHolderVar nodes in the
* parent query. (This could perhaps be done by pullup_replace_vars(),
* but it seems cleaner to use two passes.) Note in particular that any
* PlaceHolderVar nodes just created by pullup_replace_vars() will be
* adjusted, so having created them with the subquery's varno is correct.
*
* Likewise, relids appearing in AppendRelInfo nodes have to be fixed. We
* already checked that this won't require introducing multiple subrelids
* into the single-slot AppendRelInfo structs.
*/
if (parse->hasSubLinks || root->glob->lastPHId != 0 ||
root->append_rel_list)
{
Relids subrelids;
subrelids = get_relids_in_jointree((Node *) subquery->jointree, false);
substitute_phv_relids((Node *) parse, varno, subrelids);
fix_append_rel_relids(root->append_rel_list, varno, subrelids);
}
/*
* And now add subquery's AppendRelInfos to our list.
*/
root->append_rel_list = list_concat(root->append_rel_list,
subroot->append_rel_list);
/*
* We don't have to do the equivalent bookkeeping for outer-join info,
* because that hasn't been set up yet. placeholder_list likewise.
*/
Assert(root->join_info_list == NIL);
Assert(subroot->join_info_list == NIL);
Assert(root->placeholder_list == NIL);
Assert(subroot->placeholder_list == NIL);
/*
* Miscellaneous housekeeping.
*
* Although replace_rte_variables() faithfully updated parse->hasSubLinks
* if it copied any SubLinks out of the subquery's targetlist, we still
* could have SubLinks added to the query in the expressions of FUNCTION
* and VALUES RTEs copied up from the subquery. So it's necessary to copy
* subquery->hasSubLinks anyway. Perhaps this can be improved someday.
*/
parse->hasSubLinks |= subquery->hasSubLinks;
/* If subquery had any RLS conditions, now main query does too */
parse->hasRowSecurity |= subquery->hasRowSecurity;
/*
* subquery won't be pulled up if it hasAggs, hasWindowFuncs, or
* hasTargetSRFs, so no work needed on those flags
*/
/*
* Return the adjusted subquery jointree to replace the RangeTblRef entry
* in parent's jointree; or, if the FromExpr is degenerate, just return
* its single member.
*/
Assert(IsA(subquery->jointree, FromExpr));
Assert(subquery->jointree->fromlist != NIL);
if (subquery->jointree->quals == NULL &&
list_length(subquery->jointree->fromlist) == 1)
return (Node *) linitial(subquery->jointree->fromlist);
return (Node *) subquery->jointree;
}
/*
* pull_up_simple_union_all
* Pull up a single simple UNION ALL subquery.
*
* jtnode is a RangeTblRef that has been identified as a simple UNION ALL
* subquery by pull_up_subqueries. We pull up the leaf subqueries and
* build an "append relation" for the union set. The result value is just
* jtnode, since we don't actually need to change the query jointree.
*/
static Node *
pull_up_simple_union_all(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte)
{
int varno = ((RangeTblRef *) jtnode)->rtindex;
Query *subquery = rte->subquery;
int rtoffset = list_length(root->parse->rtable);
List *rtable;
/*
* Make a modifiable copy of the subquery's rtable, so we can adjust
* upper-level Vars in it. There are no such Vars in the setOperations
* tree proper, so fixing the rtable should be sufficient.
*/
rtable = copyObject(subquery->rtable);
/*
* Upper-level vars in subquery are now one level closer to their parent
* than before. We don't have to worry about offsetting varnos, though,
* because the UNION leaf queries can't cross-reference each other.
*/
IncrementVarSublevelsUp_rtable(rtable, -1, 1);
/*
* If the UNION ALL subquery had a LATERAL marker, propagate that to all
* its children. The individual children might or might not contain any
* actual lateral cross-references, but we have to mark the pulled-up
* child RTEs so that later planner stages will check for such.
*/
if (rte->lateral)
{
ListCell *rt;
foreach(rt, rtable)
{
RangeTblEntry *child_rte = (RangeTblEntry *) lfirst(rt);
Assert(child_rte->rtekind == RTE_SUBQUERY);
child_rte->lateral = true;
}
}
/*
* Append child RTEs to parent rtable.
*/
root->parse->rtable = list_concat(root->parse->rtable, rtable);
/*
* Recursively scan the subquery's setOperations tree and add
* AppendRelInfo nodes for leaf subqueries to the parent's
* append_rel_list. Also apply pull_up_subqueries to the leaf subqueries.
*/
Assert(subquery->setOperations);
pull_up_union_leaf_queries(subquery->setOperations, root, varno, subquery,
rtoffset);
/*
* Mark the parent as an append relation.
*/
rte->inh = true;
return jtnode;
}
/*
* pull_up_union_leaf_queries -- recursive guts of pull_up_simple_union_all
*
* Build an AppendRelInfo for each leaf query in the setop tree, and then
* apply pull_up_subqueries to the leaf query.
*
* Note that setOpQuery is the Query containing the setOp node, whose tlist
* contains references to all the setop output columns. When called from
* pull_up_simple_union_all, this is *not* the same as root->parse, which is
* the parent Query we are pulling up into.
*
* parentRTindex is the appendrel parent's index in root->parse->rtable.
*
* The child RTEs have already been copied to the parent. childRToffset
* tells us where in the parent's range table they were copied. When called
* from flatten_simple_union_all, childRToffset is 0 since the child RTEs
* were already in root->parse->rtable and no RT index adjustment is needed.
*/
static void
pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root, int parentRTindex,
Query *setOpQuery, int childRToffset)
{
if (IsA(setOp, RangeTblRef))
{
RangeTblRef *rtr = (RangeTblRef *) setOp;
int childRTindex;
AppendRelInfo *appinfo;
/*
* Calculate the index in the parent's range table
*/
childRTindex = childRToffset + rtr->rtindex;
/*
* Build a suitable AppendRelInfo, and attach to parent's list.
*/
appinfo = makeNode(AppendRelInfo);
appinfo->parent_relid = parentRTindex;
appinfo->child_relid = childRTindex;
appinfo->parent_reltype = InvalidOid;
appinfo->child_reltype = InvalidOid;
make_setop_translation_list(setOpQuery, childRTindex, appinfo);
appinfo->parent_reloid = InvalidOid;
root->append_rel_list = lappend(root->append_rel_list, appinfo);
/*
* Recursively apply pull_up_subqueries to the new child RTE. (We
* must build the AppendRelInfo first, because this will modify it.)
* Note that we can pass NULL for containing-join info even if we're
* actually under an outer join, because the child's expressions
* aren't going to propagate up to the join. Also, we ignore the
* possibility that pull_up_subqueries_recurse() returns a different
* jointree node than what we pass it; if it does, the important thing
* is that it replaced the child relid in the AppendRelInfo node.
*/
rtr = makeNode(RangeTblRef);
rtr->rtindex = childRTindex;
(void) pull_up_subqueries_recurse(root, (Node *) rtr,
NULL, NULL, appinfo);
}
else if (IsA(setOp, SetOperationStmt))
{
SetOperationStmt *op = (SetOperationStmt *) setOp;
/* Recurse to reach leaf queries */
pull_up_union_leaf_queries(op->larg, root, parentRTindex, setOpQuery,
childRToffset);
pull_up_union_leaf_queries(op->rarg, root, parentRTindex, setOpQuery,
childRToffset);
}
else
{
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(setOp));
}
}
/*
* make_setop_translation_list
* Build the list of translations from parent Vars to child Vars for
* a UNION ALL member. (At this point it's just a simple list of
* referencing Vars, but if we succeed in pulling up the member
* subquery, the Vars will get replaced by pulled-up expressions.)
* Also create the rather trivial reverse-translation array.
*/
static void
make_setop_translation_list(Query *query, Index newvarno,
AppendRelInfo *appinfo)
{
List *vars = NIL;
AttrNumber *pcolnos;
ListCell *l;
/* Initialize reverse-translation array with all entries zero */
/* (entries for resjunk columns will stay that way) */
appinfo->num_child_cols = list_length(query->targetList);
appinfo->parent_colnos = pcolnos =
(AttrNumber *) palloc0(appinfo->num_child_cols * sizeof(AttrNumber));
foreach(l, query->targetList)
{
TargetEntry *tle = (TargetEntry *) lfirst(l);
if (tle->resjunk)
continue;
vars = lappend(vars, makeVarFromTargetEntry(newvarno, tle));
pcolnos[tle->resno - 1] = tle->resno;
}
appinfo->translated_vars = vars;
}
/*
* is_simple_subquery
* Check a subquery in the range table to see if it's simple enough
* to pull up into the parent query.
*
* rte is the RTE_SUBQUERY RangeTblEntry that contained the subquery.
* (Note subquery is not necessarily equal to rte->subquery; it could be a
* processed copy of that.)
* lowest_outer_join is the lowest outer join above the subquery, or NULL.
*/
static bool
is_simple_subquery(PlannerInfo *root, Query *subquery, RangeTblEntry *rte,
JoinExpr *lowest_outer_join)
{
/*
* Let's just make sure it's a valid subselect ...
*/
if (!IsA(subquery, Query) ||
subquery->commandType != CMD_SELECT)
elog(ERROR, "subquery is bogus");
/*
* Can't currently pull up a query with setops (unless it's simple UNION
* ALL, which is handled by a different code path). Maybe after querytree
* redesign...
*/
if (subquery->setOperations)
return false;
/*
* Can't pull up a subquery involving grouping, aggregation, SRFs,
* sorting, limiting, or WITH. (XXX WITH could possibly be allowed later)
*
* We also don't pull up a subquery that has explicit FOR UPDATE/SHARE
* clauses, because pullup would cause the locking to occur semantically
* higher than it should. Implicit FOR UPDATE/SHARE is okay because in
* that case the locking was originally declared in the upper query
* anyway.
*/
if (subquery->hasAggs ||
subquery->hasWindowFuncs ||
subquery->hasTargetSRFs ||
subquery->groupClause ||
subquery->groupingSets ||
subquery->havingQual ||
subquery->sortClause ||
subquery->distinctClause ||
subquery->limitOffset ||
subquery->limitCount ||
subquery->hasForUpdate ||
subquery->cteList)
return false;
/*
* Don't pull up if the RTE represents a security-barrier view; we
* couldn't prevent information leakage once the RTE's Vars are scattered
* about in the upper query.
*/
if (rte->security_barrier)
return false;
/*
* If the subquery is LATERAL, check for pullup restrictions from that.
*/
if (rte->lateral)
{
bool restricted;
Relids safe_upper_varnos;
/*
* The subquery's WHERE and JOIN/ON quals mustn't contain any lateral
* references to rels outside a higher outer join (including the case
* where the outer join is within the subquery itself). In such a
* case, pulling up would result in a situation where we need to
* postpone quals from below an outer join to above it, which is
* probably completely wrong and in any case is a complication that
* doesn't seem worth addressing at the moment.
*/
if (lowest_outer_join != NULL)
{
restricted = true;
safe_upper_varnos = get_relids_in_jointree((Node *) lowest_outer_join,
true);
}
else
{
restricted = false;
safe_upper_varnos = NULL; /* doesn't matter */
}
if (jointree_contains_lateral_outer_refs(root,
(Node *) subquery->jointree,
restricted, safe_upper_varnos))
return false;
/*
* If there's an outer join above the LATERAL subquery, also disallow
* pullup if the subquery's targetlist has any references to rels
* outside the outer join, since these might get pulled into quals
* above the subquery (but in or below the outer join) and then lead
* to qual-postponement issues similar to the case checked for above.
* (We wouldn't need to prevent pullup if no such references appear in
* outer-query quals, but we don't have enough info here to check
* that. Also, maybe this restriction could be removed if we forced
* such refs to be wrapped in PlaceHolderVars, even when they're below
* the nearest outer join? But it's a pretty hokey usage, so not
* clear this is worth sweating over.)
*/
if (lowest_outer_join != NULL)
{
Relids lvarnos = pull_varnos_of_level(root,
(Node *) subquery->targetList,
1);
if (!bms_is_subset(lvarnos, safe_upper_varnos))
return false;
}
}
/*
* Don't pull up a subquery that has any volatile functions in its
* targetlist. Otherwise we might introduce multiple evaluations of these
* functions, if they get copied to multiple places in the upper query,
* leading to surprising results. (Note: the PlaceHolderVar mechanism
* doesn't quite guarantee single evaluation; else we could pull up anyway
* and just wrap such items in PlaceHolderVars ...)
*/
if (contain_volatile_functions((Node *) subquery->targetList))
return false;
return true;
}
/*
* pull_up_simple_values
* Pull up a single simple VALUES RTE.
*
* jtnode is a RangeTblRef that has been identified as a simple VALUES RTE
* by pull_up_subqueries. We always return a RangeTblRef representing a
* RESULT RTE to replace it (all failure cases should have been detected by
* is_simple_values()). Actually, what we return is just jtnode, because
* we replace the VALUES RTE in the rangetable with the RESULT RTE.
*
* rte is the RangeTblEntry referenced by jtnode. Because of the limited
* possible usage of VALUES RTEs, we do not need the remaining parameters
* of pull_up_subqueries_recurse.
*/
static Node *
pull_up_simple_values(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte)
{
Query *parse = root->parse;
int varno = ((RangeTblRef *) jtnode)->rtindex;
List *values_list;
List *tlist;
AttrNumber attrno;
pullup_replace_vars_context rvcontext;
ListCell *lc;
Assert(rte->rtekind == RTE_VALUES);
Assert(list_length(rte->values_lists) == 1);
/*
* Need a modifiable copy of the VALUES list to hack on, just in case it's
* multiply referenced.
*/
values_list = copyObject(linitial(rte->values_lists));
/*
* The VALUES RTE can't contain any Vars of level zero, let alone any that
* are join aliases, so no need to flatten join alias Vars.
*/
Assert(!contain_vars_of_level((Node *) values_list, 0));
/*
* Set up required context data for pullup_replace_vars. In particular,
* we have to make the VALUES list look like a subquery targetlist.
*/
tlist = NIL;
attrno = 1;
foreach(lc, values_list)
{
tlist = lappend(tlist,
makeTargetEntry((Expr *) lfirst(lc),
attrno,
NULL,
false));
attrno++;
}
rvcontext.root = root;
rvcontext.targetlist = tlist;
rvcontext.target_rte = rte;
rvcontext.relids = NULL;
rvcontext.outer_hasSubLinks = &parse->hasSubLinks;
rvcontext.varno = varno;
rvcontext.need_phvs = false;
rvcontext.wrap_non_vars = false;
/* initialize cache array with indexes 0 .. length(tlist) */
rvcontext.rv_cache = palloc0((list_length(tlist) + 1) *
sizeof(Node *));
/*
* Replace all of the top query's references to the RTE's outputs with
* copies of the adjusted VALUES expressions, being careful not to replace
* any of the jointree structure. We can assume there's no outer joins or
* appendrels in the dummy Query that surrounds a VALUES RTE.
*/
perform_pullup_replace_vars(root, &rvcontext, NULL, NULL);
/*
* There should be no appendrels to fix, nor any outer joins and hence no
* PlaceHolderVars.
*/
Assert(root->append_rel_list == NIL);
Assert(root->join_info_list == NIL);
Assert(root->placeholder_list == NIL);
/*
* Replace the VALUES RTE with a RESULT RTE. The VALUES RTE is the only
* rtable entry in the current query level, so this is easy.
*/
Assert(list_length(parse->rtable) == 1);
/* Create suitable RTE */
rte = makeNode(RangeTblEntry);
rte->rtekind = RTE_RESULT;
rte->eref = makeAlias("*RESULT*", NIL);
/* Replace rangetable */
parse->rtable = list_make1(rte);
/* We could manufacture a new RangeTblRef, but the one we have is fine */
Assert(varno == 1);
return jtnode;
}
/*
* is_simple_values
* Check a VALUES RTE in the range table to see if it's simple enough
* to pull up into the parent query.
*
* rte is the RTE_VALUES RangeTblEntry to check.
*/
static bool
is_simple_values(PlannerInfo *root, RangeTblEntry *rte)
{
Assert(rte->rtekind == RTE_VALUES);
/*
* There must be exactly one VALUES list, else it's not semantically
* correct to replace the VALUES RTE with a RESULT RTE, nor would we have
* a unique set of expressions to substitute into the parent query.
*/
if (list_length(rte->values_lists) != 1)
return false;
/*
* Because VALUES can't appear under an outer join (or at least, we won't
* try to pull it up if it does), we need not worry about LATERAL, nor
* about validity of PHVs for the VALUES' outputs.
*/
/*
* Don't pull up a VALUES that contains any set-returning or volatile
* functions. The considerations here are basically identical to the
* restrictions on a pull-able subquery's targetlist.
*/
if (expression_returns_set((Node *) rte->values_lists) ||
contain_volatile_functions((Node *) rte->values_lists))
return false;
/*
* Do not pull up a VALUES that's not the only RTE in its parent query.
* This is actually the only case that the parser will generate at the
* moment, and assuming this is true greatly simplifies
* pull_up_simple_values().
*/
if (list_length(root->parse->rtable) != 1 ||
rte != (RangeTblEntry *) linitial(root->parse->rtable))
return false;
return true;
}
/*
* pull_up_constant_function
* Pull up an RTE_FUNCTION expression that was simplified to a constant.
*
* jtnode is a RangeTblRef that has been identified as a FUNCTION RTE by
* pull_up_subqueries. If its expression is just a Const, hoist that value
* up into the parent query, and replace the RTE_FUNCTION with RTE_RESULT.
*
* In principle we could pull up any immutable expression, but we don't.
* That might result in multiple evaluations of the expression, which could
* be costly if it's not just a Const. Also, the main value of this is
* to let the constant participate in further const-folding, and of course
* that won't happen for a non-Const.
*
* The pulled-up value might need to be wrapped in a PlaceHolderVar if the
* RTE is below an outer join or is part of an appendrel; the extra
* parameters show whether that's needed.
*/
static Node *
pull_up_constant_function(PlannerInfo *root, Node *jtnode,
RangeTblEntry *rte,
JoinExpr *lowest_nulling_outer_join,
AppendRelInfo *containing_appendrel)
{
Query *parse = root->parse;
RangeTblFunction *rtf;
TypeFuncClass functypclass;
Oid funcrettype;
TupleDesc tupdesc;
pullup_replace_vars_context rvcontext;
/* Fail if the RTE has ORDINALITY - we don't implement that here. */
if (rte->funcordinality)
return jtnode;
/* Fail if RTE isn't a single, simple Const expr */
if (list_length(rte->functions) != 1)
return jtnode;
rtf = linitial_node(RangeTblFunction, rte->functions);
if (!IsA(rtf->funcexpr, Const))
return jtnode;
/*
* If the function's result is not a scalar, we punt. In principle we
* could break the composite constant value apart into per-column
* constants, but for now it seems not worth the work.
*/
if (rtf->funccolcount != 1)
return jtnode; /* definitely composite */
functypclass = get_expr_result_type(rtf->funcexpr,
&funcrettype,
&tupdesc);
if (functypclass != TYPEFUNC_SCALAR)
return jtnode; /* must be a one-column composite type */
/* Create context for applying pullup_replace_vars */
rvcontext.root = root;
rvcontext.targetlist = list_make1(makeTargetEntry((Expr *) rtf->funcexpr,
1, /* resno */
NULL, /* resname */
false)); /* resjunk */
rvcontext.target_rte = rte;
/*
* Since this function was reduced to a Const, it doesn't contain any
* lateral references, even if it's marked as LATERAL. This means we
* don't need to fill relids.
*/
rvcontext.relids = NULL;
rvcontext.outer_hasSubLinks = &parse->hasSubLinks;
rvcontext.varno = ((RangeTblRef *) jtnode)->rtindex;
/* these flags will be set below, if needed */
rvcontext.need_phvs = false;
rvcontext.wrap_non_vars = false;
/* initialize cache array with indexes 0 .. length(tlist) */
rvcontext.rv_cache = palloc0((list_length(rvcontext.targetlist) + 1) *
sizeof(Node *));
/*
* If we are under an outer join then non-nullable items and lateral
* references may have to be turned into PlaceHolderVars.
*/
if (lowest_nulling_outer_join != NULL)
rvcontext.need_phvs = true;
/*
* If we are dealing with an appendrel member then anything that's not a
* simple Var has to be turned into a PlaceHolderVar. (See comments in
* pull_up_simple_subquery().)
*/
if (containing_appendrel != NULL)
{
rvcontext.need_phvs = true;
rvcontext.wrap_non_vars = true;
}
/*
* If the parent query uses grouping sets, we need a PlaceHolderVar for
* anything that's not a simple Var.
*/
if (parse->groupingSets)
{
rvcontext.need_phvs = true;
rvcontext.wrap_non_vars = true;
}
/*
* Replace all of the top query's references to the RTE's output with
* copies of the funcexpr, being careful not to replace any of the
* jointree structure.
*/
perform_pullup_replace_vars(root, &rvcontext,
lowest_nulling_outer_join,
containing_appendrel);
/*
* We don't need to bother with changing PlaceHolderVars in the parent
* query. Their references to the RT index are still good for now, and
* will get removed later if we're able to drop the RTE_RESULT.
*/
/*
* Convert the RTE to be RTE_RESULT type, signifying that we don't need to
* scan it anymore, and zero out RTE_FUNCTION-specific fields. Also make
* sure the RTE is not marked LATERAL, since elsewhere we don't expect
* RTE_RESULTs to be LATERAL.
*/
rte->rtekind = RTE_RESULT;
rte->functions = NIL;
rte->lateral = false;
/*
* We can reuse the RangeTblRef node.
*/
return jtnode;
}
/*
* is_simple_union_all
* Check a subquery to see if it's a simple UNION ALL.
*
* We require all the setops to be UNION ALL (no mixing) and there can't be
* any datatype coercions involved, ie, all the leaf queries must emit the
* same datatypes.
*/
static bool
is_simple_union_all(Query *subquery)
{
SetOperationStmt *topop;
/* Let's just make sure it's a valid subselect ... */
if (!IsA(subquery, Query) ||
subquery->commandType != CMD_SELECT)
elog(ERROR, "subquery is bogus");
/* Is it a set-operation query at all? */
topop = castNode(SetOperationStmt, subquery->setOperations);
if (!topop)
return false;
/* Can't handle ORDER BY, LIMIT/OFFSET, locking, or WITH */
if (subquery->sortClause ||
subquery->limitOffset ||
subquery->limitCount ||
subquery->rowMarks ||
subquery->cteList)
return false;
/* Recursively check the tree of set operations */
return is_simple_union_all_recurse((Node *) topop, subquery,
topop->colTypes);
}
static bool
is_simple_union_all_recurse(Node *setOp, Query *setOpQuery, List *colTypes)
{
if (IsA(setOp, RangeTblRef))
{
RangeTblRef *rtr = (RangeTblRef *) setOp;
RangeTblEntry *rte = rt_fetch(rtr->rtindex, setOpQuery->rtable);
Query *subquery = rte->subquery;
Assert(subquery != NULL);
/* Leaf nodes are OK if they match the toplevel column types */
/* We don't have to compare typmods or collations here */
return tlist_same_datatypes(subquery->targetList, colTypes, true);
}
else if (IsA(setOp, SetOperationStmt))
{
SetOperationStmt *op = (SetOperationStmt *) setOp;
/* Must be UNION ALL */
if (op->op != SETOP_UNION || !op->all)
return false;
/* Recurse to check inputs */
return is_simple_union_all_recurse(op->larg, setOpQuery, colTypes) &&
is_simple_union_all_recurse(op->rarg, setOpQuery, colTypes);
}
else
{
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(setOp));
return false; /* keep compiler quiet */
}
}
/*
* is_safe_append_member
* Check a subquery that is a leaf of a UNION ALL appendrel to see if it's
* safe to pull up.
*/
static bool
is_safe_append_member(Query *subquery)
{
FromExpr *jtnode;
/*
* It's only safe to pull up the child if its jointree contains exactly
* one RTE, else the AppendRelInfo data structure breaks. The one base RTE
* could be buried in several levels of FromExpr, however. Also, if the
* child's jointree is completely empty, we can pull up because
* pull_up_simple_subquery will insert a single RTE_RESULT RTE instead.
*
* Also, the child can't have any WHERE quals because there's no place to
* put them in an appendrel. (This is a bit annoying...) If we didn't
* need to check this, we'd just test whether get_relids_in_jointree()
* yields a singleton set, to be more consistent with the coding of
* fix_append_rel_relids().
*/
jtnode = subquery->jointree;
Assert(IsA(jtnode, FromExpr));
/* Check the completely-empty case */
if (jtnode->fromlist == NIL && jtnode->quals == NULL)
return true;
/* Check the more general case */
while (IsA(jtnode, FromExpr))
{
if (jtnode->quals != NULL)
return false;
if (list_length(jtnode->fromlist) != 1)
return false;
jtnode = linitial(jtnode->fromlist);
}
if (!IsA(jtnode, RangeTblRef))
return false;
return true;
}
/*
* jointree_contains_lateral_outer_refs
* Check for disallowed lateral references in a jointree's quals
*
* If restricted is false, all level-1 Vars are allowed (but we still must
* search the jointree, since it might contain outer joins below which there
* will be restrictions). If restricted is true, return true when any qual
* in the jointree contains level-1 Vars coming from outside the rels listed
* in safe_upper_varnos.
*/
static bool
jointree_contains_lateral_outer_refs(PlannerInfo *root, Node *jtnode,
bool restricted,
Relids safe_upper_varnos)
{
if (jtnode == NULL)
return false;
if (IsA(jtnode, RangeTblRef))
return false;
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
ListCell *l;
/* First, recurse to check child joins */
foreach(l, f->fromlist)
{
if (jointree_contains_lateral_outer_refs(root,
lfirst(l),
restricted,
safe_upper_varnos))
return true;
}
/* Then check the top-level quals */
if (restricted &&
!bms_is_subset(pull_varnos_of_level(root, f->quals, 1),
safe_upper_varnos))
return true;
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
/*
* If this is an outer join, we mustn't allow any upper lateral
* references in or below it.
*/
if (j->jointype != JOIN_INNER)
{
restricted = true;
safe_upper_varnos = NULL;
}
/* Check the child joins */
if (jointree_contains_lateral_outer_refs(root,
j->larg,
restricted,
safe_upper_varnos))
return true;
if (jointree_contains_lateral_outer_refs(root,
j->rarg,
restricted,
safe_upper_varnos))
return true;
/* Check the JOIN's qual clauses */
if (restricted &&
!bms_is_subset(pull_varnos_of_level(root, j->quals, 1),
safe_upper_varnos))
return true;
}
else
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(jtnode));
return false;
}
/*
* Perform pullup_replace_vars everyplace it's needed in the query tree.
*
* Caller has already filled *rvcontext with data describing what to
* substitute for Vars referencing the target subquery. In addition
* we need the identity of the lowest outer join that can null the
* target subquery, and its containing appendrel if any.
*/
static void
perform_pullup_replace_vars(PlannerInfo *root,
pullup_replace_vars_context *rvcontext,
JoinExpr *lowest_nulling_outer_join,
AppendRelInfo *containing_appendrel)
{
Query *parse = root->parse;
ListCell *lc;
/*
* Replace all of the top query's references to the subquery's outputs
* with copies of the adjusted subtlist items, being careful not to
* replace any of the jointree structure. (This'd be a lot cleaner if we
* could use query_tree_mutator.) We have to use PHVs in the targetList,
* returningList, and havingQual, since those are certainly above any
* outer join. replace_vars_in_jointree tracks its location in the
* jointree and uses PHVs or not appropriately.
*/
parse->targetList = (List *)
pullup_replace_vars((Node *) parse->targetList, rvcontext);
parse->returningList = (List *)
pullup_replace_vars((Node *) parse->returningList, rvcontext);
if (parse->onConflict)
{
parse->onConflict->onConflictSet = (List *)
pullup_replace_vars((Node *) parse->onConflict->onConflictSet,
rvcontext);
parse->onConflict->onConflictWhere =
pullup_replace_vars(parse->onConflict->onConflictWhere,
rvcontext);
/*
* We assume ON CONFLICT's arbiterElems, arbiterWhere, exclRelTlist
* can't contain any references to a subquery.
*/
}
replace_vars_in_jointree((Node *) parse->jointree, rvcontext,
lowest_nulling_outer_join);
Assert(parse->setOperations == NULL);
parse->havingQual = pullup_replace_vars(parse->havingQual, rvcontext);
/*
* Replace references in the translated_vars lists of appendrels. When
* pulling up an appendrel member, we do not need PHVs in the list of the
* parent appendrel --- there isn't any outer join between. Elsewhere,
* use PHVs for safety. (This analysis could be made tighter but it seems
* unlikely to be worth much trouble.)
*/
foreach(lc, root->append_rel_list)
{
AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(lc);
bool save_need_phvs = rvcontext->need_phvs;
if (appinfo == containing_appendrel)
rvcontext->need_phvs = false;
appinfo->translated_vars = (List *)
pullup_replace_vars((Node *) appinfo->translated_vars, rvcontext);
rvcontext->need_phvs = save_need_phvs;
}
/*
* Replace references in the joinaliasvars lists of join RTEs.
*
* You might think that we could avoid using PHVs for alias vars of joins
* below lowest_nulling_outer_join, but that doesn't work because the
* alias vars could be referenced above that join; we need the PHVs to be
* present in such references after the alias vars get flattened. (It
* might be worth trying to be smarter here, someday.)
*/
foreach(lc, parse->rtable)
{
RangeTblEntry *otherrte = (RangeTblEntry *) lfirst(lc);
if (otherrte->rtekind == RTE_JOIN)
otherrte->joinaliasvars = (List *)
pullup_replace_vars((Node *) otherrte->joinaliasvars,
rvcontext);
}
}
/*
* Helper routine for perform_pullup_replace_vars: do pullup_replace_vars on
* every expression in the jointree, without changing the jointree structure
* itself. Ugly, but there's no other way...
*
* If we are at or below lowest_nulling_outer_join, we can suppress use of
* PlaceHolderVars wrapped around the replacement expressions.
*/
static void
replace_vars_in_jointree(Node *jtnode,
pullup_replace_vars_context *context,
JoinExpr *lowest_nulling_outer_join)
{
if (jtnode == NULL)
return;
if (IsA(jtnode, RangeTblRef))
{
/*
* If the RangeTblRef refers to a LATERAL subquery (that isn't the
* same subquery we're pulling up), it might contain references to the
* target subquery, which we must replace. We drive this from the
* jointree scan, rather than a scan of the rtable, for a couple of
* reasons: we can avoid processing no-longer-referenced RTEs, and we
* can use the appropriate setting of need_phvs depending on whether
* the RTE is above possibly-nulling outer joins or not.
*/
int varno = ((RangeTblRef *) jtnode)->rtindex;
if (varno != context->varno) /* ignore target subquery itself */
{
RangeTblEntry *rte = rt_fetch(varno, context->root->parse->rtable);
Assert(rte != context->target_rte);
if (rte->lateral)
{
switch (rte->rtekind)
{
case RTE_RELATION:
/* shouldn't be marked LATERAL unless tablesample */
Assert(rte->tablesample);
rte->tablesample = (TableSampleClause *)
pullup_replace_vars((Node *) rte->tablesample,
context);
break;
case RTE_SUBQUERY:
rte->subquery =
pullup_replace_vars_subquery(rte->subquery,
context);
break;
case RTE_FUNCTION:
rte->functions = (List *)
pullup_replace_vars((Node *) rte->functions,
context);
break;
case RTE_TABLEFUNC:
rte->tablefunc = (TableFunc *)
pullup_replace_vars((Node *) rte->tablefunc,
context);
break;
case RTE_VALUES:
rte->values_lists = (List *)
pullup_replace_vars((Node *) rte->values_lists,
context);
break;
case RTE_JOIN:
case RTE_CTE:
case RTE_NAMEDTUPLESTORE:
case RTE_RESULT:
/* these shouldn't be marked LATERAL */
Assert(false);
break;
}
}
}
}
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
ListCell *l;
foreach(l, f->fromlist)
replace_vars_in_jointree(lfirst(l), context,
lowest_nulling_outer_join);
f->quals = pullup_replace_vars(f->quals, context);
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
bool save_need_phvs = context->need_phvs;
if (j == lowest_nulling_outer_join)
{
/* no more PHVs in or below this join */
context->need_phvs = false;
lowest_nulling_outer_join = NULL;
}
replace_vars_in_jointree(j->larg, context, lowest_nulling_outer_join);
replace_vars_in_jointree(j->rarg, context, lowest_nulling_outer_join);
/*
* Use PHVs within the join quals of a full join, even when it's the
* lowest nulling outer join. Otherwise, we cannot identify which
* side of the join a pulled-up var-free expression came from, which
* can lead to failure to make a plan at all because none of the quals
* appear to be mergeable or hashable conditions. For this purpose we
* don't care about the state of wrap_non_vars, so leave it alone.
*/
if (j->jointype == JOIN_FULL)
context->need_phvs = true;
j->quals = pullup_replace_vars(j->quals, context);
/*
* We don't bother to update the colvars list, since it won't be used
* again ...
*/
context->need_phvs = save_need_phvs;
}
else
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(jtnode));
}
/*
* Apply pullup variable replacement throughout an expression tree
*
* Returns a modified copy of the tree, so this can't be used where we
* need to do in-place replacement.
*/
static Node *
pullup_replace_vars(Node *expr, pullup_replace_vars_context *context)
{
return replace_rte_variables(expr,
context->varno, 0,
pullup_replace_vars_callback,
(void *) context,
context->outer_hasSubLinks);
}
static Node *
pullup_replace_vars_callback(Var *var,
replace_rte_variables_context *context)
{
pullup_replace_vars_context *rcon = (pullup_replace_vars_context *) context->callback_arg;
int varattno = var->varattno;
Node *newnode;
/*
* If PlaceHolderVars are needed, we cache the modified expressions in
* rcon->rv_cache[]. This is not in hopes of any material speed gain
* within this function, but to avoid generating identical PHVs with
* different IDs. That would result in duplicate evaluations at runtime,
* and possibly prevent optimizations that rely on recognizing different
* references to the same subquery output as being equal(). So it's worth
* a bit of extra effort to avoid it.
*/
if (rcon->need_phvs &&
varattno >= InvalidAttrNumber &&
varattno <= list_length(rcon->targetlist) &&
rcon->rv_cache[varattno] != NULL)
{
/* Just copy the entry and fall through to adjust its varlevelsup */
newnode = copyObject(rcon->rv_cache[varattno]);
}
else if (varattno == InvalidAttrNumber)
{
/* Must expand whole-tuple reference into RowExpr */
RowExpr *rowexpr;
List *colnames;
List *fields;
bool save_need_phvs = rcon->need_phvs;
int save_sublevelsup = context->sublevels_up;
/*
* If generating an expansion for a var of a named rowtype (ie, this
* is a plain relation RTE), then we must include dummy items for
* dropped columns. If the var is RECORD (ie, this is a JOIN), then
* omit dropped columns. Either way, attach column names to the
* RowExpr for use of ruleutils.c.
*
* In order to be able to cache the results, we always generate the
* expansion with varlevelsup = 0, and then adjust if needed.
*/
expandRTE(rcon->target_rte,
var->varno, 0 /* not varlevelsup */ , var->location,
(var->vartype != RECORDOID),
&colnames, &fields);
/* Adjust the generated per-field Vars, but don't insert PHVs */
rcon->need_phvs = false;
context->sublevels_up = 0; /* to match the expandRTE output */
fields = (List *) replace_rte_variables_mutator((Node *) fields,
context);
rcon->need_phvs = save_need_phvs;
context->sublevels_up = save_sublevelsup;
rowexpr = makeNode(RowExpr);
rowexpr->args = fields;
rowexpr->row_typeid = var->vartype;
rowexpr->row_format = COERCE_IMPLICIT_CAST;
rowexpr->colnames = colnames;
rowexpr->location = var->location;
newnode = (Node *) rowexpr;
/*
* Insert PlaceHolderVar if needed. Notice that we are wrapping one
* PlaceHolderVar around the whole RowExpr, rather than putting one
* around each element of the row. This is because we need the
* expression to yield NULL, not ROW(NULL,NULL,...) when it is forced
* to null by an outer join.
*/
if (rcon->need_phvs)
{
/* RowExpr is certainly not strict, so always need PHV */
newnode = (Node *)
make_placeholder_expr(rcon->root,
(Expr *) newnode,
bms_make_singleton(rcon->varno));
/* cache it with the PHV, and with varlevelsup still zero */
rcon->rv_cache[InvalidAttrNumber] = copyObject(newnode);
}
}
else
{
/* Normal case referencing one targetlist element */
TargetEntry *tle = get_tle_by_resno(rcon->targetlist, varattno);
if (tle == NULL) /* shouldn't happen */
elog(ERROR, "could not find attribute %d in subquery targetlist",
varattno);
/* Make a copy of the tlist item to return */
newnode = (Node *) copyObject(tle->expr);
/* Insert PlaceHolderVar if needed */
if (rcon->need_phvs)
{
bool wrap;
if (newnode && IsA(newnode, Var) &&
((Var *) newnode)->varlevelsup == 0)
{
/*
* Simple Vars always escape being wrapped, unless they are
* lateral references to something outside the subquery being
* pulled up. (Even then, we could omit the PlaceHolderVar if
* the referenced rel is under the same lowest outer join, but
* it doesn't seem worth the trouble to check that.)
*/
if (rcon->target_rte->lateral &&
!bms_is_member(((Var *) newnode)->varno, rcon->relids))
wrap = true;
else
wrap = false;
}
else if (newnode && IsA(newnode, PlaceHolderVar) &&
((PlaceHolderVar *) newnode)->phlevelsup == 0)
{
/* No need to wrap a PlaceHolderVar with another one, either */
wrap = false;
}
else if (rcon->wrap_non_vars)
{
/* Wrap all non-Vars in a PlaceHolderVar */
wrap = true;
}
else
{
/*
* If it contains a Var of the subquery being pulled up, and
* does not contain any non-strict constructs, then it's
* certainly nullable so we don't need to insert a
* PlaceHolderVar.
*
* This analysis could be tighter: in particular, a non-strict
* construct hidden within a lower-level PlaceHolderVar is not
* reason to add another PHV. But for now it doesn't seem
* worth the code to be more exact.
*
* Note: in future maybe we should insert a PlaceHolderVar
* anyway, if the tlist item is expensive to evaluate?
*
* For a LATERAL subquery, we have to check the actual var
* membership of the node, but if it's non-lateral then any
* level-zero var must belong to the subquery.
*/
if ((rcon->target_rte->lateral ?
bms_overlap(pull_varnos(rcon->root, (Node *) newnode),
rcon->relids) :
contain_vars_of_level((Node *) newnode, 0)) &&
!contain_nonstrict_functions((Node *) newnode))
{
/* No wrap needed */
wrap = false;
}
else
{
/* Else wrap it in a PlaceHolderVar */
wrap = true;
}
}
if (wrap)
newnode = (Node *)
make_placeholder_expr(rcon->root,
(Expr *) newnode,
bms_make_singleton(rcon->varno));
/*
* Cache it if possible (ie, if the attno is in range, which it
* probably always should be). We can cache the value even if we
* decided we didn't need a PHV, since this result will be
* suitable for any request that has need_phvs.
*/
if (varattno > InvalidAttrNumber &&
varattno <= list_length(rcon->targetlist))
rcon->rv_cache[varattno] = copyObject(newnode);
}
}
/* Must adjust varlevelsup if tlist item is from higher query */
if (var->varlevelsup > 0)
IncrementVarSublevelsUp(newnode, var->varlevelsup, 0);
return newnode;
}
/*
* Apply pullup variable replacement to a subquery
*
* This needs to be different from pullup_replace_vars() because
* replace_rte_variables will think that it shouldn't increment sublevels_up
* before entering the Query; so we need to call it with sublevels_up == 1.
*/
static Query *
pullup_replace_vars_subquery(Query *query,
pullup_replace_vars_context *context)
{
Assert(IsA(query, Query));
return (Query *) replace_rte_variables((Node *) query,
context->varno, 1,
pullup_replace_vars_callback,
(void *) context,
NULL);
}
/*
* flatten_simple_union_all
* Try to optimize top-level UNION ALL structure into an appendrel
*
* If a query's setOperations tree consists entirely of simple UNION ALL
* operations, flatten it into an append relation, which we can process more
* intelligently than the general setops case. Otherwise, do nothing.
*
* In most cases, this can succeed only for a top-level query, because for a
* subquery in FROM, the parent query's invocation of pull_up_subqueries would
* already have flattened the UNION via pull_up_simple_union_all. But there
* are a few cases we can support here but not in that code path, for example
* when the subquery also contains ORDER BY.
*/
void
flatten_simple_union_all(PlannerInfo *root)
{
Query *parse = root->parse;
SetOperationStmt *topop;
Node *leftmostjtnode;
int leftmostRTI;
RangeTblEntry *leftmostRTE;
int childRTI;
RangeTblEntry *childRTE;
RangeTblRef *rtr;
/* Shouldn't be called unless query has setops */
topop = castNode(SetOperationStmt, parse->setOperations);
Assert(topop);
/* Can't optimize away a recursive UNION */
if (root->hasRecursion)
return;
/*
* Recursively check the tree of set operations. If not all UNION ALL
* with identical column types, punt.
*/
if (!is_simple_union_all_recurse((Node *) topop, parse, topop->colTypes))
return;
/*
* Locate the leftmost leaf query in the setops tree. The upper query's
* Vars all refer to this RTE (see transformSetOperationStmt).
*/
leftmostjtnode = topop->larg;
while (leftmostjtnode && IsA(leftmostjtnode, SetOperationStmt))
leftmostjtnode = ((SetOperationStmt *) leftmostjtnode)->larg;
Assert(leftmostjtnode && IsA(leftmostjtnode, RangeTblRef));
leftmostRTI = ((RangeTblRef *) leftmostjtnode)->rtindex;
leftmostRTE = rt_fetch(leftmostRTI, parse->rtable);
Assert(leftmostRTE->rtekind == RTE_SUBQUERY);
/*
* Make a copy of the leftmost RTE and add it to the rtable. This copy
* will represent the leftmost leaf query in its capacity as a member of
* the appendrel. The original will represent the appendrel as a whole.
* (We must do things this way because the upper query's Vars have to be
* seen as referring to the whole appendrel.)
*/
childRTE = copyObject(leftmostRTE);
parse->rtable = lappend(parse->rtable, childRTE);
childRTI = list_length(parse->rtable);
/* Modify the setops tree to reference the child copy */
((RangeTblRef *) leftmostjtnode)->rtindex = childRTI;
/* Modify the formerly-leftmost RTE to mark it as an appendrel parent */
leftmostRTE->inh = true;
/*
* Form a RangeTblRef for the appendrel, and insert it into FROM. The top
* Query of a setops tree should have had an empty FromClause initially.
*/
rtr = makeNode(RangeTblRef);
rtr->rtindex = leftmostRTI;
Assert(parse->jointree->fromlist == NIL);
parse->jointree->fromlist = list_make1(rtr);
/*
* Now pretend the query has no setops. We must do this before trying to
* do subquery pullup, because of Assert in pull_up_simple_subquery.
*/
parse->setOperations = NULL;
/*
* Build AppendRelInfo information, and apply pull_up_subqueries to the
* leaf queries of the UNION ALL. (We must do that now because they
* weren't previously referenced by the jointree, and so were missed by
* the main invocation of pull_up_subqueries.)
*/
pull_up_union_leaf_queries((Node *) topop, root, leftmostRTI, parse, 0);
}
/*
* reduce_outer_joins
* Attempt to reduce outer joins to plain inner joins.
*
* The idea here is that given a query like
* SELECT ... FROM a LEFT JOIN b ON (...) WHERE b.y = 42;
* we can reduce the LEFT JOIN to a plain JOIN if the "=" operator in WHERE
* is strict. The strict operator will always return NULL, causing the outer
* WHERE to fail, on any row where the LEFT JOIN filled in NULLs for b's
* columns. Therefore, there's no need for the join to produce null-extended
* rows in the first place --- which makes it a plain join not an outer join.
* (This scenario may not be very likely in a query written out by hand, but
* it's reasonably likely when pushing quals down into complex views.)
*
* More generally, an outer join can be reduced in strength if there is a
* strict qual above it in the qual tree that constrains a Var from the
* nullable side of the join to be non-null. (For FULL joins this applies
* to each side separately.)
*
* Another transformation we apply here is to recognize cases like
* SELECT ... FROM a LEFT JOIN b ON (a.x = b.y) WHERE b.y IS NULL;
* If the join clause is strict for b.y, then only null-extended rows could
* pass the upper WHERE, and we can conclude that what the query is really
* specifying is an anti-semijoin. We change the join type from JOIN_LEFT
* to JOIN_ANTI. The IS NULL clause then becomes redundant, and must be
* removed to prevent bogus selectivity calculations, but we leave it to
* distribute_qual_to_rels to get rid of such clauses.
*
* Also, we get rid of JOIN_RIGHT cases by flipping them around to become
* JOIN_LEFT. This saves some code here and in some later planner routines,
* but the main reason to do it is to not need to invent a JOIN_REVERSE_ANTI
* join type.
*
* To ease recognition of strict qual clauses, we require this routine to be
* run after expression preprocessing (i.e., qual canonicalization and JOIN
* alias-var expansion).
*/
void
reduce_outer_joins(PlannerInfo *root)
{
reduce_outer_joins_state *state;
/*
* To avoid doing strictness checks on more quals than necessary, we want
* to stop descending the jointree as soon as there are no outer joins
* below our current point. This consideration forces a two-pass process.
* The first pass gathers information about which base rels appear below
* each side of each join clause, and about whether there are outer
* join(s) below each side of each join clause. The second pass examines
* qual clauses and changes join types as it descends the tree.
*/
state = reduce_outer_joins_pass1((Node *) root->parse->jointree);
/* planner.c shouldn't have called me if no outer joins */
if (state == NULL || !state->contains_outer)
elog(ERROR, "so where are the outer joins?");
reduce_outer_joins_pass2((Node *) root->parse->jointree,
state, root, NULL, NIL, NIL);
}
/*
* reduce_outer_joins_pass1 - phase 1 data collection
*
* Returns a state node describing the given jointree node.
*/
static reduce_outer_joins_state *
reduce_outer_joins_pass1(Node *jtnode)
{
reduce_outer_joins_state *result;
result = (reduce_outer_joins_state *)
palloc(sizeof(reduce_outer_joins_state));
result->relids = NULL;
result->contains_outer = false;
result->sub_states = NIL;
if (jtnode == NULL)
return result;
if (IsA(jtnode, RangeTblRef))
{
int varno = ((RangeTblRef *) jtnode)->rtindex;
result->relids = bms_make_singleton(varno);
}
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
ListCell *l;
foreach(l, f->fromlist)
{
reduce_outer_joins_state *sub_state;
sub_state = reduce_outer_joins_pass1(lfirst(l));
result->relids = bms_add_members(result->relids,
sub_state->relids);
result->contains_outer |= sub_state->contains_outer;
result->sub_states = lappend(result->sub_states, sub_state);
}
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
reduce_outer_joins_state *sub_state;
/* join's own RT index is not wanted in result->relids */
if (IS_OUTER_JOIN(j->jointype))
result->contains_outer = true;
sub_state = reduce_outer_joins_pass1(j->larg);
result->relids = bms_add_members(result->relids,
sub_state->relids);
result->contains_outer |= sub_state->contains_outer;
result->sub_states = lappend(result->sub_states, sub_state);
sub_state = reduce_outer_joins_pass1(j->rarg);
result->relids = bms_add_members(result->relids,
sub_state->relids);
result->contains_outer |= sub_state->contains_outer;
result->sub_states = lappend(result->sub_states, sub_state);
}
else
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(jtnode));
return result;
}
/*
* reduce_outer_joins_pass2 - phase 2 processing
*
* jtnode: current jointree node
* state: state data collected by phase 1 for this node
* root: toplevel planner state
* nonnullable_rels: set of base relids forced non-null by upper quals
* nonnullable_vars: list of Vars forced non-null by upper quals
* forced_null_vars: list of Vars forced null by upper quals
*/
static void
reduce_outer_joins_pass2(Node *jtnode,
reduce_outer_joins_state *state,
PlannerInfo *root,
Relids nonnullable_rels,
List *nonnullable_vars,
List *forced_null_vars)
{
/*
* pass 2 should never descend as far as an empty subnode or base rel,
* because it's only called on subtrees marked as contains_outer.
*/
if (jtnode == NULL)
elog(ERROR, "reached empty jointree");
if (IsA(jtnode, RangeTblRef))
elog(ERROR, "reached base rel");
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
ListCell *l;
ListCell *s;
Relids pass_nonnullable_rels;
List *pass_nonnullable_vars;
List *pass_forced_null_vars;
/* Scan quals to see if we can add any constraints */
pass_nonnullable_rels = find_nonnullable_rels(f->quals);
pass_nonnullable_rels = bms_add_members(pass_nonnullable_rels,
nonnullable_rels);
pass_nonnullable_vars = find_nonnullable_vars(f->quals);
pass_nonnullable_vars = list_concat(pass_nonnullable_vars,
nonnullable_vars);
pass_forced_null_vars = find_forced_null_vars(f->quals);
pass_forced_null_vars = list_concat(pass_forced_null_vars,
forced_null_vars);
/* And recurse --- but only into interesting subtrees */
Assert(list_length(f->fromlist) == list_length(state->sub_states));
forboth(l, f->fromlist, s, state->sub_states)
{
reduce_outer_joins_state *sub_state = lfirst(s);
if (sub_state->contains_outer)
reduce_outer_joins_pass2(lfirst(l), sub_state, root,
pass_nonnullable_rels,
pass_nonnullable_vars,
pass_forced_null_vars);
}
bms_free(pass_nonnullable_rels);
/* can't so easily clean up var lists, unfortunately */
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
int rtindex = j->rtindex;
JoinType jointype = j->jointype;
reduce_outer_joins_state *left_state = linitial(state->sub_states);
reduce_outer_joins_state *right_state = lsecond(state->sub_states);
List *local_nonnullable_vars = NIL;
bool computed_local_nonnullable_vars = false;
/* Can we simplify this join? */
switch (jointype)
{
case JOIN_INNER:
break;
case JOIN_LEFT:
if (bms_overlap(nonnullable_rels, right_state->relids))
jointype = JOIN_INNER;
break;
case JOIN_RIGHT:
if (bms_overlap(nonnullable_rels, left_state->relids))
jointype = JOIN_INNER;
break;
case JOIN_FULL:
if (bms_overlap(nonnullable_rels, left_state->relids))
{
if (bms_overlap(nonnullable_rels, right_state->relids))
jointype = JOIN_INNER;
else
jointype = JOIN_LEFT;
}
else
{
if (bms_overlap(nonnullable_rels, right_state->relids))
jointype = JOIN_RIGHT;
}
break;
case JOIN_SEMI:
case JOIN_ANTI:
/*
* These could only have been introduced by pull_up_sublinks,
* so there's no way that upper quals could refer to their
* righthand sides, and no point in checking.
*/
break;
default:
elog(ERROR, "unrecognized join type: %d",
(int) jointype);
break;
}
/*
* Convert JOIN_RIGHT to JOIN_LEFT. Note that in the case where we
* reduced JOIN_FULL to JOIN_RIGHT, this will mean the JoinExpr no
* longer matches the internal ordering of any CoalesceExpr's built to
* represent merged join variables. We don't care about that at
* present, but be wary of it ...
*/
if (jointype == JOIN_RIGHT)
{
Node *tmparg;
tmparg = j->larg;
j->larg = j->rarg;
j->rarg = tmparg;
jointype = JOIN_LEFT;
right_state = linitial(state->sub_states);
left_state = lsecond(state->sub_states);
}
/*
* See if we can reduce JOIN_LEFT to JOIN_ANTI. This is the case if
* the join's own quals are strict for any var that was forced null by
* higher qual levels. NOTE: there are other ways that we could
* detect an anti-join, in particular if we were to check whether Vars
* coming from the RHS must be non-null because of table constraints.
* That seems complicated and expensive though (in particular, one
* would have to be wary of lower outer joins). For the moment this
* seems sufficient.
*/
if (jointype == JOIN_LEFT)
{
List *overlap;
local_nonnullable_vars = find_nonnullable_vars(j->quals);
computed_local_nonnullable_vars = true;
/*
* It's not sufficient to check whether local_nonnullable_vars and
* forced_null_vars overlap: we need to know if the overlap
* includes any RHS variables.
*/
overlap = list_intersection(local_nonnullable_vars,
forced_null_vars);
if (overlap != NIL &&
bms_overlap(pull_varnos(root, (Node *) overlap),
right_state->relids))
jointype = JOIN_ANTI;
}
/* Apply the jointype change, if any, to both jointree node and RTE */
if (rtindex && jointype != j->jointype)
{
RangeTblEntry *rte = rt_fetch(rtindex, root->parse->rtable);
Assert(rte->rtekind == RTE_JOIN);
Assert(rte->jointype == j->jointype);
rte->jointype = jointype;
}
j->jointype = jointype;
/* Only recurse if there's more to do below here */
if (left_state->contains_outer || right_state->contains_outer)
{
Relids local_nonnullable_rels;
List *local_forced_null_vars;
Relids pass_nonnullable_rels;
List *pass_nonnullable_vars;
List *pass_forced_null_vars;
/*
* If this join is (now) inner, we can add any constraints its
* quals provide to those we got from above. But if it is outer,
* we can pass down the local constraints only into the nullable
* side, because an outer join never eliminates any rows from its
* non-nullable side. Also, there is no point in passing upper
* constraints into the nullable side, since if there were any
* we'd have been able to reduce the join. (In the case of upper
* forced-null constraints, we *must not* pass them into the
* nullable side --- they either applied here, or not.) The upshot
* is that we pass either the local or the upper constraints,
* never both, to the children of an outer join.
*
* Note that a SEMI join works like an inner join here: it's okay
* to pass down both local and upper constraints. (There can't be
* any upper constraints affecting its inner side, but it's not
* worth having a separate code path to avoid passing them.)
*
* At a FULL join we just punt and pass nothing down --- is it
* possible to be smarter?
*/
if (jointype != JOIN_FULL)
{
local_nonnullable_rels = find_nonnullable_rels(j->quals);
if (!computed_local_nonnullable_vars)
local_nonnullable_vars = find_nonnullable_vars(j->quals);
local_forced_null_vars = find_forced_null_vars(j->quals);
if (jointype == JOIN_INNER || jointype == JOIN_SEMI)
{
/* OK to merge upper and local constraints */
local_nonnullable_rels = bms_add_members(local_nonnullable_rels,
nonnullable_rels);
local_nonnullable_vars = list_concat(local_nonnullable_vars,
nonnullable_vars);
local_forced_null_vars = list_concat(local_forced_null_vars,
forced_null_vars);
}
}
else
{
/* no use in calculating these */
local_nonnullable_rels = NULL;
local_forced_null_vars = NIL;
}
if (left_state->contains_outer)
{
if (jointype == JOIN_INNER || jointype == JOIN_SEMI)
{
/* pass union of local and upper constraints */
pass_nonnullable_rels = local_nonnullable_rels;
pass_nonnullable_vars = local_nonnullable_vars;
pass_forced_null_vars = local_forced_null_vars;
}
else if (jointype != JOIN_FULL) /* ie, LEFT or ANTI */
{
/* can't pass local constraints to non-nullable side */
pass_nonnullable_rels = nonnullable_rels;
pass_nonnullable_vars = nonnullable_vars;
pass_forced_null_vars = forced_null_vars;
}
else
{
/* no constraints pass through JOIN_FULL */
pass_nonnullable_rels = NULL;
pass_nonnullable_vars = NIL;
pass_forced_null_vars = NIL;
}
reduce_outer_joins_pass2(j->larg, left_state, root,
pass_nonnullable_rels,
pass_nonnullable_vars,
pass_forced_null_vars);
}
if (right_state->contains_outer)
{
if (jointype != JOIN_FULL) /* ie, INNER/LEFT/SEMI/ANTI */
{
/* pass appropriate constraints, per comment above */
pass_nonnullable_rels = local_nonnullable_rels;
pass_nonnullable_vars = local_nonnullable_vars;
pass_forced_null_vars = local_forced_null_vars;
}
else
{
/* no constraints pass through JOIN_FULL */
pass_nonnullable_rels = NULL;
pass_nonnullable_vars = NIL;
pass_forced_null_vars = NIL;
}
reduce_outer_joins_pass2(j->rarg, right_state, root,
pass_nonnullable_rels,
pass_nonnullable_vars,
pass_forced_null_vars);
}
bms_free(local_nonnullable_rels);
}
}
else
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(jtnode));
}
/*
* remove_useless_result_rtes
* Attempt to remove RTE_RESULT RTEs from the join tree.
*
* We can remove RTE_RESULT entries from the join tree using the knowledge
* that RTE_RESULT returns exactly one row and has no output columns. Hence,
* if one is inner-joined to anything else, we can delete it. Optimizations
* are also possible for some outer-join cases, as detailed below.
*
* Some of these optimizations depend on recognizing empty (constant-true)
* quals for FromExprs and JoinExprs. That makes it useful to apply this
* optimization pass after expression preprocessing, since that will have
* eliminated constant-true quals, allowing more cases to be recognized as
* optimizable. What's more, the usual reason for an RTE_RESULT to be present
* is that we pulled up a subquery or VALUES clause, thus very possibly
* replacing Vars with constants, making it more likely that a qual can be
* reduced to constant true. Also, because some optimizations depend on
* the outer-join type, it's best to have done reduce_outer_joins() first.
*
* A PlaceHolderVar referencing an RTE_RESULT RTE poses an obstacle to this
* process: we must remove the RTE_RESULT's relid from the PHV's phrels, but
* we must not reduce the phrels set to empty. If that would happen, and
* the RTE_RESULT is an immediate child of an outer join, we have to give up
* and not remove the RTE_RESULT: there is noplace else to evaluate the
* PlaceHolderVar. (That is, in such cases the RTE_RESULT *does* have output
* columns.) But if the RTE_RESULT is an immediate child of an inner join,
* we can usually change the PlaceHolderVar's phrels so as to evaluate it at
* the inner join instead. This is OK because we really only care that PHVs
* are evaluated above or below the correct outer joins. We can't, however,
* postpone the evaluation of a PHV to above where it is used; so there are
* some checks below on whether output PHVs are laterally referenced in the
* other join input rel(s).
*
* We used to try to do this work as part of pull_up_subqueries() where the
* potentially-optimizable cases get introduced; but it's way simpler, and
* more effective, to do it separately.
*/
void
remove_useless_result_rtes(PlannerInfo *root)
{
ListCell *cell;
/* Top level of jointree must always be a FromExpr */
Assert(IsA(root->parse->jointree, FromExpr));
/* Recurse ... */
root->parse->jointree = (FromExpr *)
remove_useless_results_recurse(root, (Node *) root->parse->jointree);
/* We should still have a FromExpr */
Assert(IsA(root->parse->jointree, FromExpr));
/*
* Remove any PlanRowMark referencing an RTE_RESULT RTE. We obviously
* must do that for any RTE_RESULT that we just removed. But one for a
* RTE that we did not remove can be dropped anyway: since the RTE has
* only one possible output row, there is no need for EPQ to mark and
* restore that row.
*
* It's necessary, not optional, to remove the PlanRowMark for a surviving
* RTE_RESULT RTE; otherwise we'll generate a whole-row Var for the
* RTE_RESULT, which the executor has no support for.
*/
foreach(cell, root->rowMarks)
{
PlanRowMark *rc = (PlanRowMark *) lfirst(cell);
if (rt_fetch(rc->rti, root->parse->rtable)->rtekind == RTE_RESULT)
root->rowMarks = foreach_delete_current(root->rowMarks, cell);
}
}
/*
* remove_useless_results_recurse
* Recursive guts of remove_useless_result_rtes.
*
* This recursively processes the jointree and returns a modified jointree.
*/
static Node *
remove_useless_results_recurse(PlannerInfo *root, Node *jtnode)
{
Assert(jtnode != NULL);
if (IsA(jtnode, RangeTblRef))
{
/* Can't immediately do anything with a RangeTblRef */
}
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
Relids result_relids = NULL;
ListCell *cell;
/*
* We can drop RTE_RESULT rels from the fromlist so long as at least
* one child remains, since joining to a one-row table changes
* nothing. (But we can't drop a RTE_RESULT that computes PHV(s) that
* are needed by some sibling. The cleanup transformation below would
* reassign the PHVs to be computed at the join, which is too late for
* the sibling's use.) The easiest way to mechanize this rule is to
* modify the list in-place.
*/
foreach(cell, f->fromlist)
{
Node *child = (Node *) lfirst(cell);
int varno;
/* Recursively transform child ... */
child = remove_useless_results_recurse(root, child);
/* ... and stick it back into the tree */
lfirst(cell) = child;
/*
* If it's an RTE_RESULT with at least one sibling, and no sibling
* references dependent PHVs, we can drop it. We don't yet know
* what the inner join's final relid set will be, so postpone
* cleanup of PHVs etc till after this loop.
*/
if (list_length(f->fromlist) > 1 &&
(varno = get_result_relid(root, child)) != 0 &&
!find_dependent_phvs_in_jointree(root, (Node *) f, varno))
{
f->fromlist = foreach_delete_current(f->fromlist, cell);
result_relids = bms_add_member(result_relids, varno);
}
}
/*
* Clean up if we dropped any RTE_RESULT RTEs. This is a bit
* inefficient if there's more than one, but it seems better to
* optimize the support code for the single-relid case.
*/
if (result_relids)
{
int varno = -1;
while ((varno = bms_next_member(result_relids, varno)) >= 0)
remove_result_refs(root, varno, (Node *) f);
}
/*
* If we're not at the top of the jointree, it's valid to simplify a
* degenerate FromExpr into its single child. (At the top, we must
* keep the FromExpr since Query.jointree is required to point to a
* FromExpr.)
*/
if (f != root->parse->jointree &&
f->quals == NULL &&
list_length(f->fromlist) == 1)
return (Node *) linitial(f->fromlist);
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
int varno;
/* First, recurse */
j->larg = remove_useless_results_recurse(root, j->larg);
j->rarg = remove_useless_results_recurse(root, j->rarg);
/* Apply join-type-specific optimization rules */
switch (j->jointype)
{
case JOIN_INNER:
/*
* An inner join is equivalent to a FromExpr, so if either
* side was simplified to an RTE_RESULT rel, we can replace
* the join with a FromExpr with just the other side; and if
* the qual is empty (JOIN ON TRUE) then we can omit the
* FromExpr as well.
*
* Just as in the FromExpr case, we can't simplify if the
* other input rel references any PHVs that are marked as to
* be evaluated at the RTE_RESULT rel, because we can't
* postpone their evaluation in that case. But we only have
* to check this in cases where it's syntactically legal for
* the other input to have a LATERAL reference to the
* RTE_RESULT rel. Only RHSes of inner and left joins are
* allowed to have such refs.
*/
if ((varno = get_result_relid(root, j->larg)) != 0 &&
!find_dependent_phvs_in_jointree(root, j->rarg, varno))
{
remove_result_refs(root, varno, j->rarg);
if (j->quals)
jtnode = (Node *)
makeFromExpr(list_make1(j->rarg), j->quals);
else
jtnode = j->rarg;
}
else if ((varno = get_result_relid(root, j->rarg)) != 0)
{
remove_result_refs(root, varno, j->larg);
if (j->quals)
jtnode = (Node *)
makeFromExpr(list_make1(j->larg), j->quals);
else
jtnode = j->larg;
}
break;
case JOIN_LEFT:
/*
* We can simplify this case if the RHS is an RTE_RESULT, with
* two different possibilities:
*
* If the qual is empty (JOIN ON TRUE), then the join can be
* strength-reduced to a plain inner join, since each LHS row
* necessarily has exactly one join partner. So we can always
* discard the RHS, much as in the JOIN_INNER case above.
* (Again, the LHS could not contain a lateral reference to
* the RHS.)
*
* Otherwise, it's still true that each LHS row should be
* returned exactly once, and since the RHS returns no columns
* (unless there are PHVs that have to be evaluated there), we
* don't much care if it's null-extended or not. So in this
* case also, we can just ignore the qual and discard the left
* join.
*/
if ((varno = get_result_relid(root, j->rarg)) != 0 &&
(j->quals == NULL ||
!find_dependent_phvs(root, varno)))
{
remove_result_refs(root, varno, j->larg);
jtnode = j->larg;
}
break;
case JOIN_RIGHT:
/* Mirror-image of the JOIN_LEFT case */
if ((varno = get_result_relid(root, j->larg)) != 0 &&
(j->quals == NULL ||
!find_dependent_phvs(root, varno)))
{
remove_result_refs(root, varno, j->rarg);
jtnode = j->rarg;
}
break;
case JOIN_SEMI:
/*
* We may simplify this case if the RHS is an RTE_RESULT; the
* join qual becomes effectively just a filter qual for the
* LHS, since we should either return the LHS row or not. For
* simplicity we inject the filter qual into a new FromExpr.
*
* Unlike the LEFT/RIGHT cases, we just Assert that there are
* no PHVs that need to be evaluated at the semijoin's RHS,
* since the rest of the query couldn't reference any outputs
* of the semijoin's RHS.
*/
if ((varno = get_result_relid(root, j->rarg)) != 0)
{
Assert(!find_dependent_phvs(root, varno));
remove_result_refs(root, varno, j->larg);
if (j->quals)
jtnode = (Node *)
makeFromExpr(list_make1(j->larg), j->quals);
else
jtnode = j->larg;
}
break;
case JOIN_FULL:
case JOIN_ANTI:
/* We have no special smarts for these cases */
break;
default:
elog(ERROR, "unrecognized join type: %d",
(int) j->jointype);
break;
}
}
else
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(jtnode));
return jtnode;
}
/*
* get_result_relid
* If jtnode is a RangeTblRef for an RTE_RESULT RTE, return its relid;
* otherwise return 0.
*/
static int
get_result_relid(PlannerInfo *root, Node *jtnode)
{
int varno;
if (!IsA(jtnode, RangeTblRef))
return 0;
varno = ((RangeTblRef *) jtnode)->rtindex;
if (rt_fetch(varno, root->parse->rtable)->rtekind != RTE_RESULT)
return 0;
return varno;
}
/*
* remove_result_refs
* Helper routine for dropping an unneeded RTE_RESULT RTE.
*
* This doesn't physically remove the RTE from the jointree, because that's
* more easily handled in remove_useless_results_recurse. What it does do
* is the necessary cleanup in the rest of the tree: we must adjust any PHVs
* that may reference the RTE. Be sure to call this at a point where the
* jointree is valid (no disconnected nodes).
*
* Note that we don't need to process the append_rel_list, since RTEs
* referenced directly in the jointree won't be appendrel members.
*
* varno is the RTE_RESULT's relid.
* newjtloc is the jointree location at which any PHVs referencing the
* RTE_RESULT should be evaluated instead.
*/
static void
remove_result_refs(PlannerInfo *root, int varno, Node *newjtloc)
{
/* Fix up PlaceHolderVars as needed */
/* If there are no PHVs anywhere, we can skip this bit */
if (root->glob->lastPHId != 0)
{
Relids subrelids;
subrelids = get_relids_in_jointree(newjtloc, false);
Assert(!bms_is_empty(subrelids));
substitute_phv_relids((Node *) root->parse, varno, subrelids);
fix_append_rel_relids(root->append_rel_list, varno, subrelids);
}
/*
* We also need to remove any PlanRowMark referencing the RTE, but we
* postpone that work until we return to remove_useless_result_rtes.
*/
}
/*
* find_dependent_phvs - are there any PlaceHolderVars whose relids are
* exactly the given varno?
*
* find_dependent_phvs should be used when we want to see if there are
* any such PHVs anywhere in the Query. Another use-case is to see if
* a subtree of the join tree contains such PHVs; but for that, we have
* to look not only at the join tree nodes themselves but at the
* referenced RTEs. For that, use find_dependent_phvs_in_jointree.
*/
typedef struct
{
Relids relids;
int sublevels_up;
} find_dependent_phvs_context;
static bool
find_dependent_phvs_walker(Node *node,
find_dependent_phvs_context *context)
{
if (node == NULL)
return false;
if (IsA(node, PlaceHolderVar))
{
PlaceHolderVar *phv = (PlaceHolderVar *) node;
if (phv->phlevelsup == context->sublevels_up &&
bms_equal(context->relids, phv->phrels))
return true;
/* fall through to examine children */
}
if (IsA(node, Query))
{
/* Recurse into subselects */
bool result;
context->sublevels_up++;
result = query_tree_walker((Query *) node,
find_dependent_phvs_walker,
(void *) context, 0);
context->sublevels_up--;
return result;
}
/* Shouldn't need to handle planner auxiliary nodes here */
Assert(!IsA(node, SpecialJoinInfo));
Assert(!IsA(node, AppendRelInfo));
Assert(!IsA(node, PlaceHolderInfo));
Assert(!IsA(node, MinMaxAggInfo));
return expression_tree_walker(node, find_dependent_phvs_walker,
(void *) context);
}
static bool
find_dependent_phvs(PlannerInfo *root, int varno)
{
find_dependent_phvs_context context;
/* If there are no PHVs anywhere, we needn't work hard */
if (root->glob->lastPHId == 0)
return false;
context.relids = bms_make_singleton(varno);
context.sublevels_up = 0;
return query_tree_walker(root->parse,
find_dependent_phvs_walker,
(void *) &context,
0);
}
static bool
find_dependent_phvs_in_jointree(PlannerInfo *root, Node *node, int varno)
{
find_dependent_phvs_context context;
Relids subrelids;
int relid;
/* If there are no PHVs anywhere, we needn't work hard */
if (root->glob->lastPHId == 0)
return false;
context.relids = bms_make_singleton(varno);
context.sublevels_up = 0;
/*
* See if the jointree fragment itself contains references (in join quals)
*/
if (find_dependent_phvs_walker(node, &context))
return true;
/*
* Otherwise, identify the set of referenced RTEs (we can ignore joins,
* since they should be flattened already, so their join alias lists no
* longer matter), and tediously check each RTE. We can ignore RTEs that
* are not marked LATERAL, though, since they couldn't possibly contain
* any cross-references to other RTEs.
*/
subrelids = get_relids_in_jointree(node, false);
relid = -1;
while ((relid = bms_next_member(subrelids, relid)) >= 0)
{
RangeTblEntry *rte = rt_fetch(relid, root->parse->rtable);
if (rte->lateral &&
range_table_entry_walker(rte,
find_dependent_phvs_walker,
(void *) &context,
0))
return true;
}
return false;
}
/*
* substitute_phv_relids - adjust PlaceHolderVar relid sets after pulling up
* a subquery or removing an RTE_RESULT jointree item
*
* Find any PlaceHolderVar nodes in the given tree that reference the
* pulled-up relid, and change them to reference the replacement relid(s).
*
* NOTE: although this has the form of a walker, we cheat and modify the
* nodes in-place. This should be OK since the tree was copied by
* pullup_replace_vars earlier. Avoid scribbling on the original values of
* the bitmapsets, though, because expression_tree_mutator doesn't copy those.
*/
typedef struct
{
int varno;
int sublevels_up;
Relids subrelids;
} substitute_phv_relids_context;
static bool
substitute_phv_relids_walker(Node *node,
substitute_phv_relids_context *context)
{
if (node == NULL)
return false;
if (IsA(node, PlaceHolderVar))
{
PlaceHolderVar *phv = (PlaceHolderVar *) node;
if (phv->phlevelsup == context->sublevels_up &&
bms_is_member(context->varno, phv->phrels))
{
phv->phrels = bms_union(phv->phrels,
context->subrelids);
phv->phrels = bms_del_member(phv->phrels,
context->varno);
/* Assert we haven't broken the PHV */
Assert(!bms_is_empty(phv->phrels));
}
/* fall through to examine children */
}
if (IsA(node, Query))
{
/* Recurse into subselects */
bool result;
context->sublevels_up++;
result = query_tree_walker((Query *) node,
substitute_phv_relids_walker,
(void *) context, 0);
context->sublevels_up--;
return result;
}
/* Shouldn't need to handle planner auxiliary nodes here */
Assert(!IsA(node, SpecialJoinInfo));
Assert(!IsA(node, AppendRelInfo));
Assert(!IsA(node, PlaceHolderInfo));
Assert(!IsA(node, MinMaxAggInfo));
return expression_tree_walker(node, substitute_phv_relids_walker,
(void *) context);
}
static void
substitute_phv_relids(Node *node, int varno, Relids subrelids)
{
substitute_phv_relids_context context;
context.varno = varno;
context.sublevels_up = 0;
context.subrelids = subrelids;
/*
* Must be prepared to start with a Query or a bare expression tree.
*/
query_or_expression_tree_walker(node,
substitute_phv_relids_walker,
(void *) &context,
0);
}
/*
* fix_append_rel_relids: update RT-index fields of AppendRelInfo nodes
*
* When we pull up a subquery, any AppendRelInfo references to the subquery's
* RT index have to be replaced by the substituted relid (and there had better
* be only one). We also need to apply substitute_phv_relids to their
* translated_vars lists, since those might contain PlaceHolderVars.
*
* We assume we may modify the AppendRelInfo nodes in-place.
*/
static void
fix_append_rel_relids(List *append_rel_list, int varno, Relids subrelids)
{
ListCell *l;
int subvarno = -1;
/*
* We only want to extract the member relid once, but we mustn't fail
* immediately if there are multiple members; it could be that none of the
* AppendRelInfo nodes refer to it. So compute it on first use. Note that
* bms_singleton_member will complain if set is not singleton.
*/
foreach(l, append_rel_list)
{
AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
/* The parent_relid shouldn't ever be a pullup target */
Assert(appinfo->parent_relid != varno);
if (appinfo->child_relid == varno)
{
if (subvarno < 0)
subvarno = bms_singleton_member(subrelids);
appinfo->child_relid = subvarno;
}
/* Also fix up any PHVs in its translated vars */
substitute_phv_relids((Node *) appinfo->translated_vars,
varno, subrelids);
}
}
/*
* get_relids_in_jointree: get set of RT indexes present in a jointree
*
* If include_joins is true, join RT indexes are included; if false,
* only base rels are included.
*/
Relids
get_relids_in_jointree(Node *jtnode, bool include_joins)
{
Relids result = NULL;
if (jtnode == NULL)
return result;
if (IsA(jtnode, RangeTblRef))
{
int varno = ((RangeTblRef *) jtnode)->rtindex;
result = bms_make_singleton(varno);
}
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
ListCell *l;
foreach(l, f->fromlist)
{
result = bms_join(result,
get_relids_in_jointree(lfirst(l),
include_joins));
}
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
result = get_relids_in_jointree(j->larg, include_joins);
result = bms_join(result,
get_relids_in_jointree(j->rarg, include_joins));
if (include_joins && j->rtindex)
result = bms_add_member(result, j->rtindex);
}
else
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(jtnode));
return result;
}
/*
* get_relids_for_join: get set of base RT indexes making up a join
*/
Relids
get_relids_for_join(Query *query, int joinrelid)
{
Node *jtnode;
jtnode = find_jointree_node_for_rel((Node *) query->jointree,
joinrelid);
if (!jtnode)
elog(ERROR, "could not find join node %d", joinrelid);
return get_relids_in_jointree(jtnode, false);
}
/*
* find_jointree_node_for_rel: locate jointree node for a base or join RT index
*
* Returns NULL if not found
*/
static Node *
find_jointree_node_for_rel(Node *jtnode, int relid)
{
if (jtnode == NULL)
return NULL;
if (IsA(jtnode, RangeTblRef))
{
int varno = ((RangeTblRef *) jtnode)->rtindex;
if (relid == varno)
return jtnode;
}
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
ListCell *l;
foreach(l, f->fromlist)
{
jtnode = find_jointree_node_for_rel(lfirst(l), relid);
if (jtnode)
return jtnode;
}
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
if (relid == j->rtindex)
return jtnode;
jtnode = find_jointree_node_for_rel(j->larg, relid);
if (jtnode)
return jtnode;
jtnode = find_jointree_node_for_rel(j->rarg, relid);
if (jtnode)
return jtnode;
}
else
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(jtnode));
return NULL;
}
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