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postgresql/src/include/optimizer/optimizer.h
Richard Guo 247dea89f7 Introduce an RTE for the grouping step 
If there are subqueries in the grouping expressions, each of these
subqueries in the targetlist and HAVING clause is expanded into
distinct SubPlan nodes.  As a result, only one of these SubPlan nodes
would be converted to reference to the grouping key column output by
the Agg node; others would have to get evaluated afresh.  This is not
efficient, and with grouping sets this can cause wrong results issues
in cases where they should go to NULL because they are from the wrong
grouping set.  Furthermore, during re-evaluation, these SubPlan nodes
might use nulled column values from grouping sets, which is not
correct.

This issue is not limited to subqueries.  For other types of
expressions that are part of grouping items, if they are transformed
into another form during preprocessing, they may fail to match lower
target items.  This can also lead to wrong results with grouping sets.

To fix this issue, we introduce a new kind of RTE representing the
output of the grouping step, with columns that are the Vars or
expressions being grouped on.  In the parser, we replace the grouping
expressions in the targetlist and HAVING clause with Vars referencing
this new RTE, so that the output of the parser directly expresses the
semantic requirement that the grouping expressions be gotten from the
grouping output rather than computed some other way.  In the planner,
we first preprocess all the columns of this new RTE and then replace
any Vars in the targetlist and HAVING clause that reference this new
RTE with the underlying grouping expressions, so that we will have
only one instance of a SubPlan node for each subquery contained in the
grouping expressions.

Bump catversion because this changes the querytree produced by the
parser.

Thanks to Tom Lane for the idea to invent a new kind of RTE.

Per reports from Geoff Winkless, Tobias Wendorff, Richard Guo from
various threads.

Author: Richard Guo
Reviewed-by: Ashutosh Bapat, Sutou Kouhei
Discussion: https://postgr.es/m/CAMbWs4_dp7e7oTwaiZeBX8+P1rXw4ThkZxh1QG81rhu9Z47VsQ@mail.gmail.com
2024-09-10 12:35:34 +09:00

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/*-------------------------------------------------------------------------
*
* optimizer.h
* External API for the Postgres planner.
*
* This header is meant to define everything that the core planner
* exposes for use by non-planner modules.
*
* Note that there are files outside src/backend/optimizer/ that are
* considered planner modules, because they're too much in bed with
* planner operations to be treated otherwise. FDW planning code is an
* example. For the most part, however, code outside the core planner
* should not need to include any optimizer/ header except this one.
*
* Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/optimizer/optimizer.h
*
*-------------------------------------------------------------------------
*/
#ifndef OPTIMIZER_H
#define OPTIMIZER_H
#include "nodes/parsenodes.h"
/*
* We don't want to include nodes/pathnodes.h here, because non-planner
* code should generally treat PlannerInfo as an opaque typedef.
* But we'd like such code to use that typedef name, so define the
* typedef either here or in pathnodes.h, whichever is read first.
*/
#ifndef HAVE_PLANNERINFO_TYPEDEF
typedef struct PlannerInfo PlannerInfo;
#define HAVE_PLANNERINFO_TYPEDEF 1
#endif
/* Likewise for IndexOptInfo and SpecialJoinInfo. */
#ifndef HAVE_INDEXOPTINFO_TYPEDEF
typedef struct IndexOptInfo IndexOptInfo;
#define HAVE_INDEXOPTINFO_TYPEDEF 1
#endif
#ifndef HAVE_SPECIALJOININFO_TYPEDEF
typedef struct SpecialJoinInfo SpecialJoinInfo;
#define HAVE_SPECIALJOININFO_TYPEDEF 1
#endif
/* It also seems best not to include plannodes.h, params.h, or htup.h here */
struct PlannedStmt;
struct ParamListInfoData;
struct HeapTupleData;
/* in path/clausesel.c: */
extern Selectivity clause_selectivity(PlannerInfo *root,
Node *clause,
int varRelid,
JoinType jointype,
SpecialJoinInfo *sjinfo);
extern Selectivity clause_selectivity_ext(PlannerInfo *root,
Node *clause,
int varRelid,
JoinType jointype,
SpecialJoinInfo *sjinfo,
bool use_extended_stats);
extern Selectivity clauselist_selectivity(PlannerInfo *root,
List *clauses,
int varRelid,
JoinType jointype,
SpecialJoinInfo *sjinfo);
extern Selectivity clauselist_selectivity_ext(PlannerInfo *root,
List *clauses,
int varRelid,
JoinType jointype,
SpecialJoinInfo *sjinfo,
bool use_extended_stats);
/* in path/costsize.c: */
/* widely used cost parameters */
extern PGDLLIMPORT double seq_page_cost;
extern PGDLLIMPORT double random_page_cost;
extern PGDLLIMPORT double cpu_tuple_cost;
extern PGDLLIMPORT double cpu_index_tuple_cost;
extern PGDLLIMPORT double cpu_operator_cost;
extern PGDLLIMPORT double parallel_tuple_cost;
extern PGDLLIMPORT double parallel_setup_cost;
extern PGDLLIMPORT double recursive_worktable_factor;
extern PGDLLIMPORT int effective_cache_size;
extern double clamp_row_est(double nrows);
extern int32 clamp_width_est(int64 tuple_width);
extern long clamp_cardinality_to_long(Cardinality x);
/* in path/indxpath.c: */
extern bool is_pseudo_constant_for_index(PlannerInfo *root, Node *expr,
IndexOptInfo *index);
/* in plan/planner.c: */
/* possible values for debug_parallel_query */
typedef enum
{
DEBUG_PARALLEL_OFF,
DEBUG_PARALLEL_ON,
DEBUG_PARALLEL_REGRESS,
} DebugParallelMode;
/* GUC parameters */
extern PGDLLIMPORT int debug_parallel_query;
extern PGDLLIMPORT bool parallel_leader_participation;
extern struct PlannedStmt *planner(Query *parse, const char *query_string,
int cursorOptions,
struct ParamListInfoData *boundParams);
extern Expr *expression_planner(Expr *expr);
extern Expr *expression_planner_with_deps(Expr *expr,
List **relationOids,
List **invalItems);
extern bool plan_cluster_use_sort(Oid tableOid, Oid indexOid);
extern int plan_create_index_workers(Oid tableOid, Oid indexOid);
/* in plan/setrefs.c: */
extern void extract_query_dependencies(Node *query,
List **relationOids,
List **invalItems,
bool *hasRowSecurity);
/* in prep/prepqual.c: */
extern Node *negate_clause(Node *node);
extern Expr *canonicalize_qual(Expr *qual, bool is_check);
/* in util/clauses.c: */
extern bool contain_mutable_functions(Node *clause);
extern bool contain_mutable_functions_after_planning(Expr *expr);
extern bool contain_volatile_functions(Node *clause);
extern bool contain_volatile_functions_after_planning(Expr *expr);
extern bool contain_volatile_functions_not_nextval(Node *clause);
extern Node *eval_const_expressions(PlannerInfo *root, Node *node);
extern void convert_saop_to_hashed_saop(Node *node);
extern Node *estimate_expression_value(PlannerInfo *root, Node *node);
extern Expr *evaluate_expr(Expr *expr, Oid result_type, int32 result_typmod,
Oid result_collation);
extern List *expand_function_arguments(List *args, bool include_out_arguments,
Oid result_type,
struct HeapTupleData *func_tuple);
/* in util/predtest.c: */
extern bool predicate_implied_by(List *predicate_list, List *clause_list,
bool weak);
extern bool predicate_refuted_by(List *predicate_list, List *clause_list,
bool weak);
/* in util/tlist.c: */
extern int count_nonjunk_tlist_entries(List *tlist);
extern TargetEntry *get_sortgroupref_tle(Index sortref,
List *targetList);
extern TargetEntry *get_sortgroupclause_tle(SortGroupClause *sgClause,
List *targetList);
extern Node *get_sortgroupclause_expr(SortGroupClause *sgClause,
List *targetList);
extern List *get_sortgrouplist_exprs(List *sgClauses,
List *targetList);
extern SortGroupClause *get_sortgroupref_clause(Index sortref,
List *clauses);
extern SortGroupClause *get_sortgroupref_clause_noerr(Index sortref,
List *clauses);
/* in util/var.c: */
/* Bits that can be OR'd into the flags argument of pull_var_clause() */
#define PVC_INCLUDE_AGGREGATES 0x0001 /* include Aggrefs in output list */
#define PVC_RECURSE_AGGREGATES 0x0002 /* recurse into Aggref arguments */
#define PVC_INCLUDE_WINDOWFUNCS 0x0004 /* include WindowFuncs in output list */
#define PVC_RECURSE_WINDOWFUNCS 0x0008 /* recurse into WindowFunc arguments */
#define PVC_INCLUDE_PLACEHOLDERS 0x0010 /* include PlaceHolderVars in
* output list */
#define PVC_RECURSE_PLACEHOLDERS 0x0020 /* recurse into PlaceHolderVar
* arguments */
extern Bitmapset *pull_varnos(PlannerInfo *root, Node *node);
extern Bitmapset *pull_varnos_of_level(PlannerInfo *root, Node *node, int levelsup);
extern void pull_varattnos(Node *node, Index varno, Bitmapset **varattnos);
extern List *pull_vars_of_level(Node *node, int levelsup);
extern bool contain_var_clause(Node *node);
extern bool contain_vars_of_level(Node *node, int levelsup);
extern int locate_var_of_level(Node *node, int levelsup);
extern List *pull_var_clause(Node *node, int flags);
extern Node *flatten_join_alias_vars(PlannerInfo *root, Query *query, Node *node);
extern Node *flatten_group_exprs(PlannerInfo *root, Query *query, Node *node);
#endif /* OPTIMIZER_H */
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