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Re-allow planner to use Merge Append to efficiently implement UNION.

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This reverts commit 7204f35919,
thus restoring 66c0185a3 (Allow planner to use Merge Append to
efficiently implement UNION) as well as the follow-on commits
d5d2205c8, 3b1a7eb28, 7487044d6.

Per further discussion on pgsql-release, we wish to ship beta1 with
this feature, and patch the bug that was found just before wrap,
rather than shipping beta1 with the feature reverted.
This commit is contained in:
Robert Haas
2024-05-21 12:42:27 -04:00
parent 3bd7b2f465
commit 12933dc604
18 changed files with 761 additions and 287 deletions
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116
src/backend/optimizer/plan/planner.c
View File

@@ -54,6 +54,7 @@
#include "optimizer/tlist.h"
#include "parser/analyze.h"
#include "parser/parse_agg.h"
#include "parser/parse_clause.h"
#include "parser/parse_relation.h"
#include "parser/parsetree.h"
#include "partitioning/partdesc.h"
@@ -119,12 +120,15 @@ typedef struct
{
List *activeWindows; /* active windows, if any */
grouping_sets_data *gset_data; /* grouping sets data, if any */
SetOperationStmt *setop; /* parent set operation or NULL if not a
* subquery belonging to a set operation */
} standard_qp_extra;
/* Local functions */
static Node *preprocess_expression(PlannerInfo *root, Node *expr, int kind);
static void preprocess_qual_conditions(PlannerInfo *root, Node *jtnode);
static void grouping_planner(PlannerInfo *root, double tuple_fraction);
static void grouping_planner(PlannerInfo *root, double tuple_fraction,
SetOperationStmt *setops);
static grouping_sets_data *preprocess_grouping_sets(PlannerInfo *root);
static List *remap_to_groupclause_idx(List *groupClause, List *gsets,
int *tleref_to_colnum_map);
@@ -249,6 +253,8 @@ static bool group_by_has_partkey(RelOptInfo *input_rel,
List *targetList,
List *groupClause);
static int common_prefix_cmp(const void *a, const void *b);
static List *generate_setop_child_grouplist(SetOperationStmt *op,
List *targetlist);
/*****************************************************************************
@@ -406,8 +412,7 @@ standard_planner(Query *parse, const char *query_string, int cursorOptions,
}
/* primary planning entry point (may recurse for subqueries) */
root = subquery_planner(glob, parse, NULL,
false, tuple_fraction);
root = subquery_planner(glob, parse, NULL, false, tuple_fraction, NULL);
/* Select best Path and turn it into a Plan */
final_rel = fetch_upper_rel(root, UPPERREL_FINAL, NULL);
@@ -598,6 +603,10 @@ standard_planner(Query *parse, const char *query_string, int cursorOptions,
* hasRecursion is true if this is a recursive WITH query.
* tuple_fraction is the fraction of tuples we expect will be retrieved.
* tuple_fraction is interpreted as explained for grouping_planner, below.
* setops is used for set operation subqueries to provide the subquery with
* the context in which it's being used so that Paths correctly sorted for the
* set operation can be generated. NULL when not planning a set operation
* child.
*
* Basically, this routine does the stuff that should only be done once
* per Query object. It then calls grouping_planner. At one time,
@@ -616,9 +625,9 @@ standard_planner(Query *parse, const char *query_string, int cursorOptions,
*--------------------
*/
PlannerInfo *
subquery_planner(PlannerGlobal *glob, Query *parse,
PlannerInfo *parent_root,
bool hasRecursion, double tuple_fraction)
subquery_planner(PlannerGlobal *glob, Query *parse, PlannerInfo *parent_root,
bool hasRecursion, double tuple_fraction,
SetOperationStmt *setops)
{
PlannerInfo *root;
List *newWithCheckOptions;
@@ -1077,7 +1086,7 @@ subquery_planner(PlannerGlobal *glob, Query *parse,
/*
* Do the main planning.
*/
grouping_planner(root, tuple_fraction);
grouping_planner(root, tuple_fraction, setops);
/*
* Capture the set of outer-level param IDs we have access to, for use in
@@ -1275,7 +1284,11 @@ preprocess_phv_expression(PlannerInfo *root, Expr *expr)
* 0 < tuple_fraction < 1: expect the given fraction of tuples available
* from the plan to be retrieved
* tuple_fraction >= 1: tuple_fraction is the absolute number of tuples
* expected to be retrieved (ie, a LIMIT specification)
* expected to be retrieved (ie, a LIMIT specification).
* setops is used for set operation subqueries to provide the subquery with
* the context in which it's being used so that Paths correctly sorted for the
* set operation can be generated. NULL when not planning a set operation
* child.
*
* Returns nothing; the useful output is in the Paths we attach to the
* (UPPERREL_FINAL, NULL) upperrel in *root. In addition,
@@ -1286,7 +1299,8 @@ preprocess_phv_expression(PlannerInfo *root, Expr *expr)
*--------------------
*/
static void
grouping_planner(PlannerInfo *root, double tuple_fraction)
grouping_planner(PlannerInfo *root, double tuple_fraction,
SetOperationStmt *setops)
{
Query *parse = root->parse;
int64 offset_est = 0;
@@ -1321,17 +1335,6 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
if (parse->setOperations)
{
/*
* If there's a top-level ORDER BY, assume we have to fetch all the
* tuples. This might be too simplistic given all the hackery below
* to possibly avoid the sort; but the odds of accurate estimates here
* are pretty low anyway. XXX try to get rid of this in favor of
* letting plan_set_operations generate both fast-start and
* cheapest-total paths.
*/
if (parse->sortClause)
root->tuple_fraction = 0.0;
/*
* Construct Paths for set operations. The results will not need any
* work except perhaps a top-level sort and/or LIMIT. Note that any
@@ -1501,6 +1504,12 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
qp_extra.activeWindows = activeWindows;
qp_extra.gset_data = gset_data;
/*
* If we're a subquery for a set operation, store the SetOperationStmt
* in qp_extra.
*/
qp_extra.setop = setops;
/*
* Generate the best unsorted and presorted paths for the scan/join
* portion of this Query, ie the processing represented by the
@@ -3453,6 +3462,27 @@ standard_qp_callback(PlannerInfo *root, void *extra)
parse->sortClause,
tlist);
/* setting setop_pathkeys might be useful to the union planner */
if (qp_extra->setop != NULL &&
set_operation_ordered_results_useful(qp_extra->setop))
{
List *groupClauses;
bool sortable;
groupClauses = generate_setop_child_grouplist(qp_extra->setop, tlist);
root->setop_pathkeys =
make_pathkeys_for_sortclauses_extended(root,
&groupClauses,
tlist,
false,
&sortable);
if (!sortable)
root->setop_pathkeys = NIL;
}
else
root->setop_pathkeys = NIL;
/*
* Figure out whether we want a sorted result from query_planner.
*
@@ -3462,7 +3492,9 @@ standard_qp_callback(PlannerInfo *root, void *extra)
* sortable DISTINCT clause that's more rigorous than the ORDER BY clause,
* we try to produce output that's sufficiently well sorted for the
* DISTINCT. Otherwise, if there is an ORDER BY clause, we want to sort
* by the ORDER BY clause.
* by the ORDER BY clause. Otherwise, if we're a subquery being planned
* for a set operation which can benefit from presorted results and have a
* sortable targetlist, we want to sort by the target list.
*
* Note: if we have both ORDER BY and GROUP BY, and ORDER BY is a superset
* of GROUP BY, it would be tempting to request sort by ORDER BY --- but
@@ -3480,6 +3512,8 @@ standard_qp_callback(PlannerInfo *root, void *extra)
root->query_pathkeys = root->distinct_pathkeys;
else if (root->sort_pathkeys)
root->query_pathkeys = root->sort_pathkeys;
else if (root->setop_pathkeys != NIL)
root->query_pathkeys = root->setop_pathkeys;
else
root->query_pathkeys = NIL;
}
@@ -7923,3 +7957,43 @@ group_by_has_partkey(RelOptInfo *input_rel,
return true;
}
/*
* generate_setop_child_grouplist
* Build a SortGroupClause list defining the sort/grouping properties
* of the child of a set operation.
*
* This is similar to generate_setop_grouplist() but differs as the setop
* child query's targetlist entries may already have a tleSortGroupRef
* assigned for other purposes, such as GROUP BYs. Here we keep the
* SortGroupClause list in the same order as 'op' groupClauses and just adjust
* the tleSortGroupRef to reference the TargetEntry's 'ressortgroupref'.
*/
static List *
generate_setop_child_grouplist(SetOperationStmt *op, List *targetlist)
{
List *grouplist = copyObject(op->groupClauses);
ListCell *lg;
ListCell *lt;
lg = list_head(grouplist);
foreach(lt, targetlist)
{
TargetEntry *tle = (TargetEntry *) lfirst(lt);
SortGroupClause *sgc;
/* resjunk columns could have sortgrouprefs. Leave these alone */
if (tle->resjunk)
continue;
/* we expect every non-resjunk target to have a SortGroupClause */
Assert(lg != NULL);
sgc = (SortGroupClause *) lfirst(lg);
lg = lnext(grouplist, lg);
/* assign a tleSortGroupRef, or reuse the existing one */
sgc->tleSortGroupRef = assignSortGroupRef(tle, targetlist);
}
Assert(lg == NULL);
return grouplist;
}