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postgres/src/backend/rewrite/rewriteHandler.c
Peter Eisentraut b9b4f10b5b Message style improvements
2006-10-06 17:14:01 +00:00

1844 lines
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/*-------------------------------------------------------------------------
*
* rewriteHandler.c
* Primary module of query rewriter.
*
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/rewrite/rewriteHandler.c,v 1.168 2006/10/06 17:13:59 petere Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/heapam.h"
#include "catalog/pg_type.h"
#include "nodes/makefuncs.h"
#include "optimizer/clauses.h"
#include "parser/analyze.h"
#include "parser/parse_coerce.h"
#include "parser/parse_expr.h"
#include "parser/parsetree.h"
#include "rewrite/rewriteHandler.h"
#include "rewrite/rewriteManip.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
/* We use a list of these to detect recursion in RewriteQuery */
typedef struct rewrite_event
{
Oid relation; /* OID of relation having rules */
CmdType event; /* type of rule being fired */
} rewrite_event;
static bool acquireLocksOnSubLinks(Node *node, void *context);
static Query *rewriteRuleAction(Query *parsetree,
Query *rule_action,
Node *rule_qual,
int rt_index,
CmdType event,
bool *returning_flag);
static List *adjustJoinTreeList(Query *parsetree, bool removert, int rt_index);
static void rewriteTargetList(Query *parsetree, Relation target_relation,
List **attrno_list);
static TargetEntry *process_matched_tle(TargetEntry *src_tle,
TargetEntry *prior_tle,
const char *attrName);
static Node *get_assignment_input(Node *node);
static void rewriteValuesRTE(RangeTblEntry *rte, Relation target_relation,
List *attrnos);
static void markQueryForLocking(Query *qry, bool forUpdate, bool noWait,
bool skipOldNew);
static List *matchLocks(CmdType event, RuleLock *rulelocks,
int varno, Query *parsetree);
static Query *fireRIRrules(Query *parsetree, List *activeRIRs);
/*
* AcquireRewriteLocks -
* Acquire suitable locks on all the relations mentioned in the Query.
* These locks will ensure that the relation schemas don't change under us
* while we are rewriting and planning the query.
*
* A secondary purpose of this routine is to fix up JOIN RTE references to
* dropped columns (see details below). Because the RTEs are modified in
* place, it is generally appropriate for the caller of this routine to have
* first done a copyObject() to make a writable copy of the querytree in the
* current memory context.
*
* This processing can, and for efficiency's sake should, be skipped when the
* querytree has just been built by the parser: parse analysis already got
* all the same locks we'd get here, and the parser will have omitted dropped
* columns from JOINs to begin with. But we must do this whenever we are
* dealing with a querytree produced earlier than the current command.
*
* About JOINs and dropped columns: although the parser never includes an
* already-dropped column in a JOIN RTE's alias var list, it is possible for
* such a list in a stored rule to include references to dropped columns.
* (If the column is not explicitly referenced anywhere else in the query,
* the dependency mechanism won't consider it used by the rule and so won't
* prevent the column drop.) To support get_rte_attribute_is_dropped(),
* we replace join alias vars that reference dropped columns with NULL Const
* nodes.
*
* (In PostgreSQL 8.0, we did not do this processing but instead had
* get_rte_attribute_is_dropped() recurse to detect dropped columns in joins.
* That approach had horrible performance unfortunately; in particular
* construction of a nested join was O(N^2) in the nesting depth.)
*/
void
AcquireRewriteLocks(Query *parsetree)
{
ListCell *l;
int rt_index;
/*
* First, process RTEs of the current query level.
*/
rt_index = 0;
foreach(l, parsetree->rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
Relation rel;
LOCKMODE lockmode;
List *newaliasvars;
Index curinputvarno;
RangeTblEntry *curinputrte;
ListCell *ll;
++rt_index;
switch (rte->rtekind)
{
case RTE_RELATION:
/*
* Grab the appropriate lock type for the relation, and do not
* release it until end of transaction. This protects the
* rewriter and planner against schema changes mid-query.
*
* If the relation is the query's result relation, then we
* need RowExclusiveLock. Otherwise, check to see if the
* relation is accessed FOR UPDATE/SHARE or not. We can't
* just grab AccessShareLock because then the executor would
* be trying to upgrade the lock, leading to possible
* deadlocks.
*/
if (rt_index == parsetree->resultRelation)
lockmode = RowExclusiveLock;
else if (get_rowmark(parsetree, rt_index))
lockmode = RowShareLock;
else
lockmode = AccessShareLock;
rel = heap_open(rte->relid, lockmode);
heap_close(rel, NoLock);
break;
case RTE_JOIN:
/*
* Scan the join's alias var list to see if any columns have
* been dropped, and if so replace those Vars with NULL
* Consts.
*
* Since a join has only two inputs, we can expect to see
* multiple references to the same input RTE; optimize away
* multiple fetches.
*/
newaliasvars = NIL;
curinputvarno = 0;
curinputrte = NULL;
foreach(ll, rte->joinaliasvars)
{
Var *aliasvar = (Var *) lfirst(ll);
/*
* If the list item isn't a simple Var, then it must
* represent a merged column, ie a USING column, and so it
* couldn't possibly be dropped, since it's referenced in
* the join clause. (Conceivably it could also be a NULL
* constant already? But that's OK too.)
*/
if (IsA(aliasvar, Var))
{
/*
* The elements of an alias list have to refer to
* earlier RTEs of the same rtable, because that's the
* order the planner builds things in. So we already
* processed the referenced RTE, and so it's safe to
* use get_rte_attribute_is_dropped on it. (This might
* not hold after rewriting or planning, but it's OK
* to assume here.)
*/
Assert(aliasvar->varlevelsup == 0);
if (aliasvar->varno != curinputvarno)
{
curinputvarno = aliasvar->varno;
if (curinputvarno >= rt_index)
elog(ERROR, "unexpected varno %d in JOIN RTE %d",
curinputvarno, rt_index);
curinputrte = rt_fetch(curinputvarno,
parsetree->rtable);
}
if (get_rte_attribute_is_dropped(curinputrte,
aliasvar->varattno))
{
/*
* can't use vartype here, since that might be a
* now-dropped type OID, but it doesn't really
* matter what type the Const claims to be.
*/
aliasvar = (Var *) makeNullConst(INT4OID);
}
}
newaliasvars = lappend(newaliasvars, aliasvar);
}
rte->joinaliasvars = newaliasvars;
break;
case RTE_SUBQUERY:
/*
* The subquery RTE itself is all right, but we have to
* recurse to process the represented subquery.
*/
AcquireRewriteLocks(rte->subquery);
break;
default:
/* ignore other types of RTEs */
break;
}
}
/*
* Recurse into sublink subqueries, too. But we already did the ones in
* the rtable.
*/
if (parsetree->hasSubLinks)
query_tree_walker(parsetree, acquireLocksOnSubLinks, NULL,
QTW_IGNORE_RT_SUBQUERIES);
}
/*
* Walker to find sublink subqueries for AcquireRewriteLocks
*/
static bool
acquireLocksOnSubLinks(Node *node, void *context)
{
if (node == NULL)
return false;
if (IsA(node, SubLink))
{
SubLink *sub = (SubLink *) node;
/* Do what we came for */
AcquireRewriteLocks((Query *) sub->subselect);
/* Fall through to process lefthand args of SubLink */
}
/*
* Do NOT recurse into Query nodes, because AcquireRewriteLocks already
* processed subselects of subselects for us.
*/
return expression_tree_walker(node, acquireLocksOnSubLinks, context);
}
/*
* rewriteRuleAction -
* Rewrite the rule action with appropriate qualifiers (taken from
* the triggering query).
*
* Input arguments:
* parsetree - original query
* rule_action - one action (query) of a rule
* rule_qual - WHERE condition of rule, or NULL if unconditional
* rt_index - RT index of result relation in original query
* event - type of rule event
* Output arguments:
* *returning_flag - set TRUE if we rewrite RETURNING clause in rule_action
* (must be initialized to FALSE)
* Return value:
* rewritten form of rule_action
*/
static Query *
rewriteRuleAction(Query *parsetree,
Query *rule_action,
Node *rule_qual,
int rt_index,
CmdType event,
bool *returning_flag)
{
int current_varno,
new_varno;
int rt_length;
Query *sub_action;
Query **sub_action_ptr;
/*
* Make modifiable copies of rule action and qual (what we're passed are
* the stored versions in the relcache; don't touch 'em!).
*/
rule_action = (Query *) copyObject(rule_action);
rule_qual = (Node *) copyObject(rule_qual);
/*
* Acquire necessary locks and fix any deleted JOIN RTE entries.
*/
AcquireRewriteLocks(rule_action);
(void) acquireLocksOnSubLinks(rule_qual, NULL);
current_varno = rt_index;
rt_length = list_length(parsetree->rtable);
new_varno = PRS2_NEW_VARNO + rt_length;
/*
* Adjust rule action and qual to offset its varnos, so that we can merge
* its rtable with the main parsetree's rtable.
*
* If the rule action is an INSERT...SELECT, the OLD/NEW rtable entries
* will be in the SELECT part, and we have to modify that rather than the
* top-level INSERT (kluge!).
*/
sub_action = getInsertSelectQuery(rule_action, &sub_action_ptr);
OffsetVarNodes((Node *) sub_action, rt_length, 0);
OffsetVarNodes(rule_qual, rt_length, 0);
/* but references to *OLD* should point at original rt_index */
ChangeVarNodes((Node *) sub_action,
PRS2_OLD_VARNO + rt_length, rt_index, 0);
ChangeVarNodes(rule_qual,
PRS2_OLD_VARNO + rt_length, rt_index, 0);
/*
* Generate expanded rtable consisting of main parsetree's rtable plus
* rule action's rtable; this becomes the complete rtable for the rule
* action. Some of the entries may be unused after we finish rewriting,
* but we leave them all in place for two reasons:
*
* We'd have a much harder job to adjust the query's varnos if we
* selectively removed RT entries.
*
* If the rule is INSTEAD, then the original query won't be executed at
* all, and so its rtable must be preserved so that the executor will do
* the correct permissions checks on it.
*
* RT entries that are not referenced in the completed jointree will be
* ignored by the planner, so they do not affect query semantics. But any
* permissions checks specified in them will be applied during executor
* startup (see ExecCheckRTEPerms()). This allows us to check that the
* caller has, say, insert-permission on a view, when the view is not
* semantically referenced at all in the resulting query.
*
* When a rule is not INSTEAD, the permissions checks done on its copied
* RT entries will be redundant with those done during execution of the
* original query, but we don't bother to treat that case differently.
*
* NOTE: because planner will destructively alter rtable, we must ensure
* that rule action's rtable is separate and shares no substructure with
* the main rtable. Hence do a deep copy here.
*/
sub_action->rtable = list_concat((List *) copyObject(parsetree->rtable),
sub_action->rtable);
/*
* Each rule action's jointree should be the main parsetree's jointree
* plus that rule's jointree, but usually *without* the original rtindex
* that we're replacing (if present, which it won't be for INSERT). Note
* that if the rule action refers to OLD, its jointree will add a
* reference to rt_index. If the rule action doesn't refer to OLD, but
* either the rule_qual or the user query quals do, then we need to keep
* the original rtindex in the jointree to provide data for the quals. We
* don't want the original rtindex to be joined twice, however, so avoid
* keeping it if the rule action mentions it.
*
* As above, the action's jointree must not share substructure with the
* main parsetree's.
*/
if (sub_action->commandType != CMD_UTILITY)
{
bool keeporig;
List *newjointree;
Assert(sub_action->jointree != NULL);
keeporig = (!rangeTableEntry_used((Node *) sub_action->jointree,
rt_index, 0)) &&
(rangeTableEntry_used(rule_qual, rt_index, 0) ||
rangeTableEntry_used(parsetree->jointree->quals, rt_index, 0));
newjointree = adjustJoinTreeList(parsetree, !keeporig, rt_index);
if (newjointree != NIL)
{
/*
* If sub_action is a setop, manipulating its jointree will do no
* good at all, because the jointree is dummy. (Perhaps someday
* we could push the joining and quals down to the member
* statements of the setop?)
*/
if (sub_action->setOperations != NULL)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("conditional UNION/INTERSECT/EXCEPT statements are not implemented")));
sub_action->jointree->fromlist =
list_concat(newjointree, sub_action->jointree->fromlist);
/*
* There could have been some SubLinks in newjointree, in which
* case we'd better mark the sub_action correctly.
*/
if (parsetree->hasSubLinks && !sub_action->hasSubLinks)
sub_action->hasSubLinks =
checkExprHasSubLink((Node *) newjointree);
}
}
/*
* Event Qualification forces copying of parsetree and splitting into two
* queries one w/rule_qual, one w/NOT rule_qual. Also add user query qual
* onto rule action
*/
AddQual(sub_action, rule_qual);
AddQual(sub_action, parsetree->jointree->quals);
/*
* Rewrite new.attribute w/ right hand side of target-list entry for
* appropriate field name in insert/update.
*
* KLUGE ALERT: since ResolveNew returns a mutated copy, we can't just
* apply it to sub_action; we have to remember to update the sublink
* inside rule_action, too.
*/
if ((event == CMD_INSERT || event == CMD_UPDATE) &&
sub_action->commandType != CMD_UTILITY)
{
sub_action = (Query *) ResolveNew((Node *) sub_action,
new_varno,
0,
rt_fetch(new_varno,
sub_action->rtable),
parsetree->targetList,
event,
current_varno);
if (sub_action_ptr)
*sub_action_ptr = sub_action;
else
rule_action = sub_action;
}
/*
* If rule_action has a RETURNING clause, then either throw it away if the
* triggering query has no RETURNING clause, or rewrite it to emit what
* the triggering query's RETURNING clause asks for. Throw an error if
* more than one rule has a RETURNING clause.
*/
if (!parsetree->returningList)
rule_action->returningList = NIL;
else if (rule_action->returningList)
{
if (*returning_flag)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot have RETURNING lists in multiple rules")));
*returning_flag = true;
rule_action->returningList = (List *)
ResolveNew((Node *) parsetree->returningList,
parsetree->resultRelation,
0,
rt_fetch(parsetree->resultRelation,
parsetree->rtable),
rule_action->returningList,
CMD_SELECT,
0);
}
return rule_action;
}
/*
* Copy the query's jointree list, and optionally attempt to remove any
* occurrence of the given rt_index as a top-level join item (we do not look
* for it within join items; this is OK because we are only expecting to find
* it as an UPDATE or DELETE target relation, which will be at the top level
* of the join). Returns modified jointree list --- this is a separate copy
* sharing no nodes with the original.
*/
static List *
adjustJoinTreeList(Query *parsetree, bool removert, int rt_index)
{
List *newjointree = copyObject(parsetree->jointree->fromlist);
ListCell *l;
if (removert)
{
foreach(l, newjointree)
{
RangeTblRef *rtr = lfirst(l);
if (IsA(rtr, RangeTblRef) &&
rtr->rtindex == rt_index)
{
newjointree = list_delete_ptr(newjointree, rtr);
/*
* foreach is safe because we exit loop after list_delete...
*/
break;
}
}
}
return newjointree;
}
/*
* rewriteTargetList - rewrite INSERT/UPDATE targetlist into standard form
*
* This has the following responsibilities:
*
* 1. For an INSERT, add tlist entries to compute default values for any
* attributes that have defaults and are not assigned to in the given tlist.
* (We do not insert anything for default-less attributes, however. The
* planner will later insert NULLs for them, but there's no reason to slow
* down rewriter processing with extra tlist nodes.) Also, for both INSERT
* and UPDATE, replace explicit DEFAULT specifications with column default
* expressions.
*
* 2. Merge multiple entries for the same target attribute, or declare error
* if we can't. Multiple entries are only allowed for INSERT/UPDATE of
* portions of an array or record field, for example
* UPDATE table SET foo[2] = 42, foo[4] = 43;
* We can merge such operations into a single assignment op. Essentially,
* the expression we want to produce in this case is like
* foo = array_set(array_set(foo, 2, 42), 4, 43)
*
* 3. Sort the tlist into standard order: non-junk fields in order by resno,
* then junk fields (these in no particular order).
*
* We must do items 1 and 2 before firing rewrite rules, else rewritten
* references to NEW.foo will produce wrong or incomplete results. Item 3
* is not needed for rewriting, but will be needed by the planner, and we
* can do it essentially for free while handling items 1 and 2.
*
* If attrno_list isn't NULL, we return an additional output besides the
* rewritten targetlist: an integer list of the assigned-to attnums, in
* order of the original tlist's non-junk entries. This is needed for
* processing VALUES RTEs.
*/
static void
rewriteTargetList(Query *parsetree, Relation target_relation,
List **attrno_list)
{
CmdType commandType = parsetree->commandType;
TargetEntry **new_tles;
List *new_tlist = NIL;
List *junk_tlist = NIL;
Form_pg_attribute att_tup;
int attrno,
next_junk_attrno,
numattrs;
ListCell *temp;
if (attrno_list) /* initialize optional result list */
*attrno_list = NIL;
/*
* We process the normal (non-junk) attributes by scanning the input tlist
* once and transferring TLEs into an array, then scanning the array to
* build an output tlist. This avoids O(N^2) behavior for large numbers
* of attributes.
*
* Junk attributes are tossed into a separate list during the same tlist
* scan, then appended to the reconstructed tlist.
*/
numattrs = RelationGetNumberOfAttributes(target_relation);
new_tles = (TargetEntry **) palloc0(numattrs * sizeof(TargetEntry *));
next_junk_attrno = numattrs + 1;
foreach(temp, parsetree->targetList)
{
TargetEntry *old_tle = (TargetEntry *) lfirst(temp);
if (!old_tle->resjunk)
{
/* Normal attr: stash it into new_tles[] */
attrno = old_tle->resno;
if (attrno < 1 || attrno > numattrs)
elog(ERROR, "bogus resno %d in targetlist", attrno);
att_tup = target_relation->rd_att->attrs[attrno - 1];
/* put attrno into attrno_list even if it's dropped */
if (attrno_list)
*attrno_list = lappend_int(*attrno_list, attrno);
/* We can (and must) ignore deleted attributes */
if (att_tup->attisdropped)
continue;
/* Merge with any prior assignment to same attribute */
new_tles[attrno - 1] =
process_matched_tle(old_tle,
new_tles[attrno - 1],
NameStr(att_tup->attname));
}
else
{
/*
* Copy all resjunk tlist entries to junk_tlist, and assign them
* resnos above the last real resno.
*
* Typical junk entries include ORDER BY or GROUP BY expressions
* (are these actually possible in an INSERT or UPDATE?), system
* attribute references, etc.
*/
/* Get the resno right, but don't copy unnecessarily */
if (old_tle->resno != next_junk_attrno)
{
old_tle = flatCopyTargetEntry(old_tle);
old_tle->resno = next_junk_attrno;
}
junk_tlist = lappend(junk_tlist, old_tle);
next_junk_attrno++;
}
}
for (attrno = 1; attrno <= numattrs; attrno++)
{
TargetEntry *new_tle = new_tles[attrno - 1];
att_tup = target_relation->rd_att->attrs[attrno - 1];
/* We can (and must) ignore deleted attributes */
if (att_tup->attisdropped)
continue;
/*
* Handle the two cases where we need to insert a default expression:
* it's an INSERT and there's no tlist entry for the column, or the
* tlist entry is a DEFAULT placeholder node.
*/
if ((new_tle == NULL && commandType == CMD_INSERT) ||
(new_tle && new_tle->expr && IsA(new_tle->expr, SetToDefault)))
{
Node *new_expr;
new_expr = build_column_default(target_relation, attrno);
/*
* If there is no default (ie, default is effectively NULL), we
* can omit the tlist entry in the INSERT case, since the planner
* can insert a NULL for itself, and there's no point in spending
* any more rewriter cycles on the entry. But in the UPDATE case
* we've got to explicitly set the column to NULL.
*/
if (!new_expr)
{
if (commandType == CMD_INSERT)
new_tle = NULL;
else
{
new_expr = (Node *) makeConst(att_tup->atttypid,
att_tup->attlen,
(Datum) 0,
true, /* isnull */
att_tup->attbyval);
/* this is to catch a NOT NULL domain constraint */
new_expr = coerce_to_domain(new_expr,
InvalidOid, -1,
att_tup->atttypid,
COERCE_IMPLICIT_CAST,
false,
false);
}
}
if (new_expr)
new_tle = makeTargetEntry((Expr *) new_expr,
attrno,
pstrdup(NameStr(att_tup->attname)),
false);
}
if (new_tle)
new_tlist = lappend(new_tlist, new_tle);
}
pfree(new_tles);
parsetree->targetList = list_concat(new_tlist, junk_tlist);
}
/*
* Convert a matched TLE from the original tlist into a correct new TLE.
*
* This routine detects and handles multiple assignments to the same target
* attribute. (The attribute name is needed only for error messages.)
*/
static TargetEntry *
process_matched_tle(TargetEntry *src_tle,
TargetEntry *prior_tle,
const char *attrName)
{
TargetEntry *result;
Node *src_expr;
Node *prior_expr;
Node *src_input;
Node *prior_input;
Node *priorbottom;
Node *newexpr;
if (prior_tle == NULL)
{
/*
* Normal case where this is the first assignment to the attribute.
*/
return src_tle;
}
/*----------
* Multiple assignments to same attribute. Allow only if all are
* FieldStore or ArrayRef assignment operations. This is a bit
* tricky because what we may actually be looking at is a nest of
* such nodes; consider
* UPDATE tab SET col.fld1.subfld1 = x, col.fld2.subfld2 = y
* The two expressions produced by the parser will look like
* FieldStore(col, fld1, FieldStore(placeholder, subfld1, x))
* FieldStore(col, fld2, FieldStore(placeholder, subfld2, x))
* However, we can ignore the substructure and just consider the top
* FieldStore or ArrayRef from each assignment, because it works to
* combine these as
* FieldStore(FieldStore(col, fld1,
* FieldStore(placeholder, subfld1, x)),
* fld2, FieldStore(placeholder, subfld2, x))
* Note the leftmost expression goes on the inside so that the
* assignments appear to occur left-to-right.
*
* For FieldStore, instead of nesting we can generate a single
* FieldStore with multiple target fields. We must nest when
* ArrayRefs are involved though.
*----------
*/
src_expr = (Node *) src_tle->expr;
prior_expr = (Node *) prior_tle->expr;
src_input = get_assignment_input(src_expr);
prior_input = get_assignment_input(prior_expr);
if (src_input == NULL ||
prior_input == NULL ||
exprType(src_expr) != exprType(prior_expr))
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("multiple assignments to same column \"%s\"",
attrName)));
/*
* Prior TLE could be a nest of assignments if we do this more than once.
*/
priorbottom = prior_input;
for (;;)
{
Node *newbottom = get_assignment_input(priorbottom);
if (newbottom == NULL)
break; /* found the original Var reference */
priorbottom = newbottom;
}
if (!equal(priorbottom, src_input))
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("multiple assignments to same column \"%s\"",
attrName)));
/*
* Looks OK to nest 'em.
*/
if (IsA(src_expr, FieldStore))
{
FieldStore *fstore = makeNode(FieldStore);
if (IsA(prior_expr, FieldStore))
{
/* combine the two */
memcpy(fstore, prior_expr, sizeof(FieldStore));
fstore->newvals =
list_concat(list_copy(((FieldStore *) prior_expr)->newvals),
list_copy(((FieldStore *) src_expr)->newvals));
fstore->fieldnums =
list_concat(list_copy(((FieldStore *) prior_expr)->fieldnums),
list_copy(((FieldStore *) src_expr)->fieldnums));
}
else
{
/* general case, just nest 'em */
memcpy(fstore, src_expr, sizeof(FieldStore));
fstore->arg = (Expr *) prior_expr;
}
newexpr = (Node *) fstore;
}
else if (IsA(src_expr, ArrayRef))
{
ArrayRef *aref = makeNode(ArrayRef);
memcpy(aref, src_expr, sizeof(ArrayRef));
aref->refexpr = (Expr *) prior_expr;
newexpr = (Node *) aref;
}
else
{
elog(ERROR, "can't happen");
newexpr = NULL;
}
result = flatCopyTargetEntry(src_tle);
result->expr = (Expr *) newexpr;
return result;
}
/*
* If node is an assignment node, return its input; else return NULL
*/
static Node *
get_assignment_input(Node *node)
{
if (node == NULL)
return NULL;
if (IsA(node, FieldStore))
{
FieldStore *fstore = (FieldStore *) node;
return (Node *) fstore->arg;
}
else if (IsA(node, ArrayRef))
{
ArrayRef *aref = (ArrayRef *) node;
if (aref->refassgnexpr == NULL)
return NULL;
return (Node *) aref->refexpr;
}
return NULL;
}
/*
* Make an expression tree for the default value for a column.
*
* If there is no default, return a NULL instead.
*/
Node *
build_column_default(Relation rel, int attrno)
{
TupleDesc rd_att = rel->rd_att;
Form_pg_attribute att_tup = rd_att->attrs[attrno - 1];
Oid atttype = att_tup->atttypid;
int32 atttypmod = att_tup->atttypmod;
Node *expr = NULL;
Oid exprtype;
/*
* Scan to see if relation has a default for this column.
*/
if (rd_att->constr && rd_att->constr->num_defval > 0)
{
AttrDefault *defval = rd_att->constr->defval;
int ndef = rd_att->constr->num_defval;
while (--ndef >= 0)
{
if (attrno == defval[ndef].adnum)
{
/*
* Found it, convert string representation to node tree.
*/
expr = stringToNode(defval[ndef].adbin);
break;
}
}
}
if (expr == NULL)
{
/*
* No per-column default, so look for a default for the type itself.
*/
expr = get_typdefault(atttype);
}
if (expr == NULL)
return NULL; /* No default anywhere */
/*
* Make sure the value is coerced to the target column type; this will
* generally be true already, but there seem to be some corner cases
* involving domain defaults where it might not be true. This should match
* the parser's processing of non-defaulted expressions --- see
* transformAssignedExpr().
*/
exprtype = exprType(expr);
expr = coerce_to_target_type(NULL, /* no UNKNOWN params here */
expr, exprtype,
atttype, atttypmod,
COERCION_ASSIGNMENT,
COERCE_IMPLICIT_CAST);
if (expr == NULL)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg("column \"%s\" is of type %s"
" but default expression is of type %s",
NameStr(att_tup->attname),
format_type_be(atttype),
format_type_be(exprtype)),
errhint("You will need to rewrite or cast the expression.")));
return expr;
}
/* Does VALUES RTE contain any SetToDefault items? */
static bool
searchForDefault(RangeTblEntry *rte)
{
ListCell *lc;
foreach(lc, rte->values_lists)
{
List *sublist = (List *) lfirst(lc);
ListCell *lc2;
foreach(lc2, sublist)
{
Node *col = (Node *) lfirst(lc2);
if (IsA(col, SetToDefault))
return true;
}
}
return false;
}
/*
* When processing INSERT ... VALUES with a VALUES RTE (ie, multiple VALUES
* lists), we have to replace any DEFAULT items in the VALUES lists with
* the appropriate default expressions. The other aspects of rewriteTargetList
* need be applied only to the query's targetlist proper.
*
* Note that we currently can't support subscripted or field assignment
* in the multi-VALUES case. The targetlist will contain simple Vars
* referencing the VALUES RTE, and therefore process_matched_tle() will
* reject any such attempt with "multiple assignments to same column".
*/
static void
rewriteValuesRTE(RangeTblEntry *rte, Relation target_relation, List *attrnos)
{
List *newValues;
ListCell *lc;
/*
* Rebuilding all the lists is a pretty expensive proposition in a big
* VALUES list, and it's a waste of time if there aren't any DEFAULT
* placeholders. So first scan to see if there are any.
*/
if (!searchForDefault(rte))
return; /* nothing to do */
/* Check list lengths (we can assume all the VALUES sublists are alike) */
Assert(list_length(attrnos) == list_length(linitial(rte->values_lists)));
newValues = NIL;
foreach(lc, rte->values_lists)
{
List *sublist = (List *) lfirst(lc);
List *newList = NIL;
ListCell *lc2;
ListCell *lc3;
forboth(lc2, sublist, lc3, attrnos)
{
Node *col = (Node *) lfirst(lc2);
int attrno = lfirst_int(lc3);
if (IsA(col, SetToDefault))
{
Form_pg_attribute att_tup;
Node *new_expr;
att_tup = target_relation->rd_att->attrs[attrno - 1];
if (!att_tup->attisdropped)
new_expr = build_column_default(target_relation, attrno);
else
new_expr = NULL; /* force a NULL if dropped */
/*
* If there is no default (ie, default is effectively NULL),
* we've got to explicitly set the column to NULL.
*/
if (!new_expr)
{
new_expr = (Node *) makeConst(att_tup->atttypid,
att_tup->attlen,
(Datum) 0,
true, /* isnull */
att_tup->attbyval);
/* this is to catch a NOT NULL domain constraint */
new_expr = coerce_to_domain(new_expr,
InvalidOid, -1,
att_tup->atttypid,
COERCE_IMPLICIT_CAST,
false,
false);
}
newList = lappend(newList, new_expr);
}
else
newList = lappend(newList, col);
}
newValues = lappend(newValues, newList);
}
rte->values_lists = newValues;
}
/*
* matchLocks -
* match the list of locks and returns the matching rules
*/
static List *
matchLocks(CmdType event,
RuleLock *rulelocks,
int varno,
Query *parsetree)
{
List *matching_locks = NIL;
int nlocks;
int i;
if (rulelocks == NULL)
return NIL;
if (parsetree->commandType != CMD_SELECT)
{
if (parsetree->resultRelation != varno)
return NIL;
}
nlocks = rulelocks->numLocks;
for (i = 0; i < nlocks; i++)
{
RewriteRule *oneLock = rulelocks->rules[i];
if (oneLock->event == event)
{
if (parsetree->commandType != CMD_SELECT ||
(oneLock->attrno == -1 ?
rangeTableEntry_used((Node *) parsetree, varno, 0) :
attribute_used((Node *) parsetree,
varno, oneLock->attrno, 0)))
matching_locks = lappend(matching_locks, oneLock);
}
}
return matching_locks;
}
/*
* ApplyRetrieveRule - expand an ON SELECT rule
*/
static Query *
ApplyRetrieveRule(Query *parsetree,
RewriteRule *rule,
int rt_index,
bool relation_level,
Relation relation,
List *activeRIRs)
{
Query *rule_action;
RangeTblEntry *rte,
*subrte;
RowMarkClause *rc;
if (list_length(rule->actions) != 1)
elog(ERROR, "expected just one rule action");
if (rule->qual != NULL)
elog(ERROR, "cannot handle qualified ON SELECT rule");
if (!relation_level)
elog(ERROR, "cannot handle per-attribute ON SELECT rule");
/*
* Make a modifiable copy of the view query, and acquire needed locks on
* the relations it mentions.
*/
rule_action = copyObject(linitial(rule->actions));
AcquireRewriteLocks(rule_action);
/*
* Recursively expand any view references inside the view.
*/
rule_action = fireRIRrules(rule_action, activeRIRs);
/*
* VIEWs are really easy --- just plug the view query in as a subselect,
* replacing the relation's original RTE.
*/
rte = rt_fetch(rt_index, parsetree->rtable);
rte->rtekind = RTE_SUBQUERY;
rte->relid = InvalidOid;
rte->subquery = rule_action;
rte->inh = false; /* must not be set for a subquery */
/*
* We move the view's permission check data down to its rangetable. The
* checks will actually be done against the *OLD* entry therein.
*/
subrte = rt_fetch(PRS2_OLD_VARNO, rule_action->rtable);
Assert(subrte->relid == relation->rd_id);
subrte->requiredPerms = rte->requiredPerms;
subrte->checkAsUser = rte->checkAsUser;
rte->requiredPerms = 0; /* no permission check on subquery itself */
rte->checkAsUser = InvalidOid;
/*
* FOR UPDATE/SHARE of view?
*/
if ((rc = get_rowmark(parsetree, rt_index)) != NULL)
{
/*
* Remove the view from the list of rels that will actually be marked
* FOR UPDATE/SHARE by the executor. It will still be access-checked
* for write access, though.
*/
parsetree->rowMarks = list_delete_ptr(parsetree->rowMarks, rc);
/*
* Set up the view's referenced tables as if FOR UPDATE/SHARE.
*/
markQueryForLocking(rule_action, rc->forUpdate,
rc->noWait, true);
}
return parsetree;
}
/*
* Recursively mark all relations used by a view as FOR UPDATE/SHARE.
*
* This may generate an invalid query, eg if some sub-query uses an
* aggregate. We leave it to the planner to detect that.
*
* NB: this must agree with the parser's transformLocking() routine.
*/
static void
markQueryForLocking(Query *qry, bool forUpdate, bool noWait, bool skipOldNew)
{
Index rti = 0;
ListCell *l;
foreach(l, qry->rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
rti++;
/* Ignore OLD and NEW entries if we are at top level of view */
if (skipOldNew &&
(rti == PRS2_OLD_VARNO || rti == PRS2_NEW_VARNO))
continue;
if (rte->rtekind == RTE_RELATION)
{
applyLockingClause(qry, rti, forUpdate, noWait);
rte->requiredPerms |= ACL_SELECT_FOR_UPDATE;
}
else if (rte->rtekind == RTE_SUBQUERY)
{
/* FOR UPDATE/SHARE of subquery is propagated to subquery's rels */
markQueryForLocking(rte->subquery, forUpdate, noWait, false);
}
}
}
/*
* fireRIRonSubLink -
* Apply fireRIRrules() to each SubLink (subselect in expression) found
* in the given tree.
*
* NOTE: although this has the form of a walker, we cheat and modify the
* SubLink nodes in-place. It is caller's responsibility to ensure that
* no unwanted side-effects occur!
*
* This is unlike most of the other routines that recurse into subselects,
* because we must take control at the SubLink node in order to replace
* the SubLink's subselect link with the possibly-rewritten subquery.
*/
static bool
fireRIRonSubLink(Node *node, List *activeRIRs)
{
if (node == NULL)
return false;
if (IsA(node, SubLink))
{
SubLink *sub = (SubLink *) node;
/* Do what we came for */
sub->subselect = (Node *) fireRIRrules((Query *) sub->subselect,
activeRIRs);
/* Fall through to process lefthand args of SubLink */
}
/*
* Do NOT recurse into Query nodes, because fireRIRrules already processed
* subselects of subselects for us.
*/
return expression_tree_walker(node, fireRIRonSubLink,
(void *) activeRIRs);
}
/*
* fireRIRrules -
* Apply all RIR rules on each rangetable entry in a query
*/
static Query *
fireRIRrules(Query *parsetree, List *activeRIRs)
{
int rt_index;
/*
* don't try to convert this into a foreach loop, because rtable list can
* get changed each time through...
*/
rt_index = 0;
while (rt_index < list_length(parsetree->rtable))
{
RangeTblEntry *rte;
Relation rel;
List *locks;
RuleLock *rules;
RewriteRule *rule;
int i;
++rt_index;
rte = rt_fetch(rt_index, parsetree->rtable);
/*
* A subquery RTE can't have associated rules, so there's nothing to
* do to this level of the query, but we must recurse into the
* subquery to expand any rule references in it.
*/
if (rte->rtekind == RTE_SUBQUERY)
{
rte->subquery = fireRIRrules(rte->subquery, activeRIRs);
continue;
}
/*
* Joins and other non-relation RTEs can be ignored completely.
*/
if (rte->rtekind != RTE_RELATION)
continue;
/*
* If the table is not referenced in the query, then we ignore it.
* This prevents infinite expansion loop due to new rtable entries
* inserted by expansion of a rule. A table is referenced if it is
* part of the join set (a source table), or is referenced by any Var
* nodes, or is the result table.
*/
if (rt_index != parsetree->resultRelation &&
!rangeTableEntry_used((Node *) parsetree, rt_index, 0))
continue;
/*
* We can use NoLock here since either the parser or
* AcquireRewriteLocks should have locked the rel already.
*/
rel = heap_open(rte->relid, NoLock);
/*
* Collect the RIR rules that we must apply
*/
rules = rel->rd_rules;
if (rules == NULL)
{
heap_close(rel, NoLock);
continue;
}
locks = NIL;
for (i = 0; i < rules->numLocks; i++)
{
rule = rules->rules[i];
if (rule->event != CMD_SELECT)
continue;
if (rule->attrno > 0)
{
/* per-attr rule; do we need it? */
if (!attribute_used((Node *) parsetree, rt_index,
rule->attrno, 0))
continue;
}
locks = lappend(locks, rule);
}
/*
* If we found any, apply them --- but first check for recursion!
*/
if (locks != NIL)
{
ListCell *l;
if (list_member_oid(activeRIRs, RelationGetRelid(rel)))
ereport(ERROR,
(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
errmsg("infinite recursion detected in rules for relation \"%s\"",
RelationGetRelationName(rel))));
activeRIRs = lcons_oid(RelationGetRelid(rel), activeRIRs);
foreach(l, locks)
{
rule = lfirst(l);
parsetree = ApplyRetrieveRule(parsetree,
rule,
rt_index,
rule->attrno == -1,
rel,
activeRIRs);
}
activeRIRs = list_delete_first(activeRIRs);
}
heap_close(rel, NoLock);
}
/*
* Recurse into sublink subqueries, too. But we already did the ones in
* the rtable.
*/
if (parsetree->hasSubLinks)
query_tree_walker(parsetree, fireRIRonSubLink, (void *) activeRIRs,
QTW_IGNORE_RT_SUBQUERIES);
return parsetree;
}
/*
* Modify the given query by adding 'AND rule_qual IS NOT TRUE' to its
* qualification. This is used to generate suitable "else clauses" for
* conditional INSTEAD rules. (Unfortunately we must use "x IS NOT TRUE",
* not just "NOT x" which the planner is much smarter about, else we will
* do the wrong thing when the qual evaluates to NULL.)
*
* The rule_qual may contain references to OLD or NEW. OLD references are
* replaced by references to the specified rt_index (the relation that the
* rule applies to). NEW references are only possible for INSERT and UPDATE
* queries on the relation itself, and so they should be replaced by copies
* of the related entries in the query's own targetlist.
*/
static Query *
CopyAndAddInvertedQual(Query *parsetree,
Node *rule_qual,
int rt_index,
CmdType event)
{
/* Don't scribble on the passed qual (it's in the relcache!) */
Node *new_qual = (Node *) copyObject(rule_qual);
/*
* In case there are subqueries in the qual, acquire necessary locks and
* fix any deleted JOIN RTE entries. (This is somewhat redundant with
* rewriteRuleAction, but not entirely ... consider restructuring so that
* we only need to process the qual this way once.)
*/
(void) acquireLocksOnSubLinks(new_qual, NULL);
/* Fix references to OLD */
ChangeVarNodes(new_qual, PRS2_OLD_VARNO, rt_index, 0);
/* Fix references to NEW */
if (event == CMD_INSERT || event == CMD_UPDATE)
new_qual = ResolveNew(new_qual,
PRS2_NEW_VARNO,
0,
rt_fetch(rt_index, parsetree->rtable),
parsetree->targetList,
event,
rt_index);
/* And attach the fixed qual */
AddInvertedQual(parsetree, new_qual);
return parsetree;
}
/*
* fireRules -
* Iterate through rule locks applying rules.
*
* Input arguments:
* parsetree - original query
* rt_index - RT index of result relation in original query
* event - type of rule event
* locks - list of rules to fire
* Output arguments:
* *instead_flag - set TRUE if any unqualified INSTEAD rule is found
* (must be initialized to FALSE)
* *returning_flag - set TRUE if we rewrite RETURNING clause in any rule
* (must be initialized to FALSE)
* *qual_product - filled with modified original query if any qualified
* INSTEAD rule is found (must be initialized to NULL)
* Return value:
* list of rule actions adjusted for use with this query
*
* Qualified INSTEAD rules generate their action with the qualification
* condition added. They also generate a modified version of the original
* query with the negated qualification added, so that it will run only for
* rows that the qualified action doesn't act on. (If there are multiple
* qualified INSTEAD rules, we AND all the negated quals onto a single
* modified original query.) We won't execute the original, unmodified
* query if we find either qualified or unqualified INSTEAD rules. If
* we find both, the modified original query is discarded too.
*/
static List *
fireRules(Query *parsetree,
int rt_index,
CmdType event,
List *locks,
bool *instead_flag,
bool *returning_flag,
Query **qual_product)
{
List *results = NIL;
ListCell *l;
foreach(l, locks)
{
RewriteRule *rule_lock = (RewriteRule *) lfirst(l);
Node *event_qual = rule_lock->qual;
List *actions = rule_lock->actions;
QuerySource qsrc;
ListCell *r;
/* Determine correct QuerySource value for actions */
if (rule_lock->isInstead)
{
if (event_qual != NULL)
qsrc = QSRC_QUAL_INSTEAD_RULE;
else
{
qsrc = QSRC_INSTEAD_RULE;
*instead_flag = true; /* report unqualified INSTEAD */
}
}
else
qsrc = QSRC_NON_INSTEAD_RULE;
if (qsrc == QSRC_QUAL_INSTEAD_RULE)
{
/*
* If there are INSTEAD rules with qualifications, the original
* query is still performed. But all the negated rule
* qualifications of the INSTEAD rules are added so it does its
* actions only in cases where the rule quals of all INSTEAD rules
* are false. Think of it as the default action in a case. We save
* this in *qual_product so RewriteQuery() can add it to the query
* list after we mangled it up enough.
*
* If we have already found an unqualified INSTEAD rule, then
* *qual_product won't be used, so don't bother building it.
*/
if (!*instead_flag)
{
if (*qual_product == NULL)
*qual_product = copyObject(parsetree);
*qual_product = CopyAndAddInvertedQual(*qual_product,
event_qual,
rt_index,
event);
}
}
/* Now process the rule's actions and add them to the result list */
foreach(r, actions)
{
Query *rule_action = lfirst(r);
if (rule_action->commandType == CMD_NOTHING)
continue;
rule_action = rewriteRuleAction(parsetree, rule_action,
event_qual, rt_index, event,
returning_flag);
rule_action->querySource = qsrc;
rule_action->canSetTag = false; /* might change later */
results = lappend(results, rule_action);
}
}
return results;
}
/*
* RewriteQuery -
* rewrites the query and apply the rules again on the queries rewritten
*
* rewrite_events is a list of open query-rewrite actions, so we can detect
* infinite recursion.
*/
static List *
RewriteQuery(Query *parsetree, List *rewrite_events)
{
CmdType event = parsetree->commandType;
bool instead = false;
bool returning = false;
Query *qual_product = NULL;
List *rewritten = NIL;
/*
* If the statement is an update, insert or delete - fire rules on it.
*
* SELECT rules are handled later when we have all the queries that should
* get executed. Also, utilities aren't rewritten at all (do we still
* need that check?)
*/
if (event != CMD_SELECT && event != CMD_UTILITY)
{
int result_relation;
RangeTblEntry *rt_entry;
Relation rt_entry_relation;
List *locks;
result_relation = parsetree->resultRelation;
Assert(result_relation != 0);
rt_entry = rt_fetch(result_relation, parsetree->rtable);
Assert(rt_entry->rtekind == RTE_RELATION);
/*
* We can use NoLock here since either the parser or
* AcquireRewriteLocks should have locked the rel already.
*/
rt_entry_relation = heap_open(rt_entry->relid, NoLock);
/*
* If it's an INSERT or UPDATE, rewrite the targetlist into standard
* form. This will be needed by the planner anyway, and doing it now
* ensures that any references to NEW.field will behave sanely.
*/
if (event == CMD_UPDATE)
rewriteTargetList(parsetree, rt_entry_relation, NULL);
else if (event == CMD_INSERT)
{
RangeTblEntry *values_rte = NULL;
/*
* If it's an INSERT ... VALUES (...), (...), ... there will be a
* single RTE for the VALUES targetlists.
*/
if (list_length(parsetree->jointree->fromlist) == 1)
{
RangeTblRef *rtr = (RangeTblRef *) linitial(parsetree->jointree->fromlist);
if (IsA(rtr, RangeTblRef))
{
RangeTblEntry *rte = rt_fetch(rtr->rtindex,
parsetree->rtable);
if (rte->rtekind == RTE_VALUES)
values_rte = rte;
}
}
if (values_rte)
{
List *attrnos;
/* Process the main targetlist ... */
rewriteTargetList(parsetree, rt_entry_relation, &attrnos);
/* ... and the VALUES expression lists */
rewriteValuesRTE(values_rte, rt_entry_relation, attrnos);
}
else
{
/* Process just the main targetlist */
rewriteTargetList(parsetree, rt_entry_relation, NULL);
}
}
/*
* Collect and apply the appropriate rules.
*/
locks = matchLocks(event, rt_entry_relation->rd_rules,
result_relation, parsetree);
if (locks != NIL)
{
List *product_queries;
product_queries = fireRules(parsetree,
result_relation,
event,
locks,
&instead,
&returning,
&qual_product);
/*
* If we got any product queries, recursively rewrite them --- but
* first check for recursion!
*/
if (product_queries != NIL)
{
ListCell *n;
rewrite_event *rev;
foreach(n, rewrite_events)
{
rev = (rewrite_event *) lfirst(n);
if (rev->relation == RelationGetRelid(rt_entry_relation) &&
rev->event == event)
ereport(ERROR,
(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
errmsg("infinite recursion detected in rules for relation \"%s\"",
RelationGetRelationName(rt_entry_relation))));
}
rev = (rewrite_event *) palloc(sizeof(rewrite_event));
rev->relation = RelationGetRelid(rt_entry_relation);
rev->event = event;
rewrite_events = lcons(rev, rewrite_events);
foreach(n, product_queries)
{
Query *pt = (Query *) lfirst(n);
List *newstuff;
newstuff = RewriteQuery(pt, rewrite_events);
rewritten = list_concat(rewritten, newstuff);
}
rewrite_events = list_delete_first(rewrite_events);
}
}
/*
* If there is an INSTEAD, and the original query has a RETURNING, we
* have to have found a RETURNING in the rule(s), else fail. (Because
* DefineQueryRewrite only allows RETURNING in unconditional INSTEAD
* rules, there's no need to worry whether the substituted RETURNING
* will actually be executed --- it must be.)
*/
if ((instead || qual_product != NULL) &&
parsetree->returningList &&
!returning)
{
switch (event)
{
case CMD_INSERT:
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot perform INSERT RETURNING on relation \"%s\"",
RelationGetRelationName(rt_entry_relation)),
errhint("You need an unconditional ON INSERT DO INSTEAD rule with a RETURNING clause.")));
break;
case CMD_UPDATE:
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot perform UPDATE RETURNING on relation \"%s\"",
RelationGetRelationName(rt_entry_relation)),
errhint("You need an unconditional ON UPDATE DO INSTEAD rule with a RETURNING clause.")));
break;
case CMD_DELETE:
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot perform DELETE RETURNING on relation \"%s\"",
RelationGetRelationName(rt_entry_relation)),
errhint("You need an unconditional ON DELETE DO INSTEAD rule with a RETURNING clause.")));
break;
default:
elog(ERROR, "unrecognized commandType: %d",
(int) event);
break;
}
}
heap_close(rt_entry_relation, NoLock);
}
/*
* For INSERTs, the original query is done first; for UPDATE/DELETE, it is
* done last. This is needed because update and delete rule actions might
* not do anything if they are invoked after the update or delete is
* performed. The command counter increment between the query executions
* makes the deleted (and maybe the updated) tuples disappear so the scans
* for them in the rule actions cannot find them.
*
* If we found any unqualified INSTEAD, the original query is not done at
* all, in any form. Otherwise, we add the modified form if qualified
* INSTEADs were found, else the unmodified form.
*/
if (!instead)
{
if (parsetree->commandType == CMD_INSERT)
{
if (qual_product != NULL)
rewritten = lcons(qual_product, rewritten);
else
rewritten = lcons(parsetree, rewritten);
}
else
{
if (qual_product != NULL)
rewritten = lappend(rewritten, qual_product);
else
rewritten = lappend(rewritten, parsetree);
}
}
return rewritten;
}
/*
* QueryRewrite -
* Primary entry point to the query rewriter.
* Rewrite one query via query rewrite system, possibly returning 0
* or many queries.
*
* NOTE: the parsetree must either have come straight from the parser,
* or have been scanned by AcquireRewriteLocks to acquire suitable locks.
*/
List *
QueryRewrite(Query *parsetree)
{
List *querylist;
List *results = NIL;
ListCell *l;
CmdType origCmdType;
bool foundOriginalQuery;
Query *lastInstead;
/*
* Step 1
*
* Apply all non-SELECT rules possibly getting 0 or many queries
*/
querylist = RewriteQuery(parsetree, NIL);
/*
* Step 2
*
* Apply all the RIR rules on each query
*/
foreach(l, querylist)
{
Query *query = (Query *) lfirst(l);
query = fireRIRrules(query, NIL);
/*
* If the query target was rewritten as a view, complain.
*/
if (query->resultRelation)
{
RangeTblEntry *rte = rt_fetch(query->resultRelation,
query->rtable);
if (rte->rtekind == RTE_SUBQUERY)
{
switch (query->commandType)
{
case CMD_INSERT:
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot insert into a view"),
errhint("You need an unconditional ON INSERT DO INSTEAD rule.")));
break;
case CMD_UPDATE:
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot update a view"),
errhint("You need an unconditional ON UPDATE DO INSTEAD rule.")));
break;
case CMD_DELETE:
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot delete from a view"),
errhint("You need an unconditional ON DELETE DO INSTEAD rule.")));
break;
default:
elog(ERROR, "unrecognized commandType: %d",
(int) query->commandType);
break;
}
}
}
results = lappend(results, query);
}
/*
* Step 3
*
* Determine which, if any, of the resulting queries is supposed to set
* the command-result tag; and update the canSetTag fields accordingly.
*
* If the original query is still in the list, it sets the command tag.
* Otherwise, the last INSTEAD query of the same kind as the original is
* allowed to set the tag. (Note these rules can leave us with no query
* setting the tag. The tcop code has to cope with this by setting up a
* default tag based on the original un-rewritten query.)
*
* The Asserts verify that at most one query in the result list is marked
* canSetTag. If we aren't checking asserts, we can fall out of the loop
* as soon as we find the original query.
*/
origCmdType = parsetree->commandType;
foundOriginalQuery = false;
lastInstead = NULL;
foreach(l, results)
{
Query *query = (Query *) lfirst(l);
if (query->querySource == QSRC_ORIGINAL)
{
Assert(query->canSetTag);
Assert(!foundOriginalQuery);
foundOriginalQuery = true;
#ifndef USE_ASSERT_CHECKING
break;
#endif
}
else
{
Assert(!query->canSetTag);
if (query->commandType == origCmdType &&
(query->querySource == QSRC_INSTEAD_RULE ||
query->querySource == QSRC_QUAL_INSTEAD_RULE))
lastInstead = query;
}
}
if (!foundOriginalQuery && lastInstead != NULL)
lastInstead->canSetTag = true;
return results;
}
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