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08d2d58a2a
postgresql/contrib/postgres_fdw/postgres_fdw.h
Etsuro Fujita 08d2d58a2a postgres_fdw: Fix costing of pre-sorted foreign paths with local stats. 
Commit aa09cd242 modified estimate_path_cost_size() so that it reuses
cached costs of a basic foreign path for a given foreign-base/join
relation when costing pre-sorted foreign paths for that relation, but it
incorrectly re-computed retrieved_rows, an estimated number of rows
fetched from the remote side, which is needed for costing both the basic
and pre-sorted foreign paths.  To fix, handle retrieved_rows the same way
as the cached costs: store in that relation's fpinfo the retrieved_rows
estimate computed for costing the basic foreign path, and reuse it when
costing the pre-sorted foreign paths.  Also, reuse the rows/width
estimates stored in that relation's fpinfo when costing the pre-sorted
foreign paths, to make the code consistent.

In commit ffab494a4, to extend the costing mentioned above to the
foreign-grouping case, I made a change to add_foreign_grouping_paths() to
store in a given foreign-grouped relation's RelOptInfo the rows estimate
for that relation for reuse, but this patch makes that change unnecessary
since we already store the row estimate in that relation's fpinfo, which
this patch reuses when costing a foreign path for that relation with the
sortClause ordering; remove that change.

In passing, fix thinko in commit 7012b132d: in estimate_path_cost_size(),
the width estimate for a given foreign-grouped relation to be stored in
that relation's fpinfo was reset incorrectly when costing a basic foreign
path for that relation with local stats.

Apply the patch to HEAD only to avoid destabilizing existing plan choices.

Author: Etsuro Fujita
Discussion: https://postgr.es/m/CAPmGK17jaJLPDEkgnP2VmkOg=5wT8YQ1CqssU8JRpZ_NSE+dqQ@mail.gmail.com
2019-06-14 20:49:59 +09:00

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/*-------------------------------------------------------------------------
*
* postgres_fdw.h
* Foreign-data wrapper for remote PostgreSQL servers
*
* Portions Copyright (c) 2012-2019, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/postgres_fdw/postgres_fdw.h
*
*-------------------------------------------------------------------------
*/
#ifndef POSTGRES_FDW_H
#define POSTGRES_FDW_H
#include "foreign/foreign.h"
#include "lib/stringinfo.h"
#include "nodes/pathnodes.h"
#include "utils/relcache.h"
#include "libpq-fe.h"
/*
* FDW-specific planner information kept in RelOptInfo.fdw_private for a
* postgres_fdw foreign table. For a baserel, this struct is created by
* postgresGetForeignRelSize, although some fields are not filled till later.
* postgresGetForeignJoinPaths creates it for a joinrel, and
* postgresGetForeignUpperPaths creates it for an upperrel.
*/
typedef struct PgFdwRelationInfo
{
/*
* True means that the relation can be pushed down. Always true for simple
* foreign scan.
*/
bool pushdown_safe;
/*
* Restriction clauses, divided into safe and unsafe to pushdown subsets.
* All entries in these lists should have RestrictInfo wrappers; that
* improves efficiency of selectivity and cost estimation.
*/
List *remote_conds;
List *local_conds;
/* Actual remote restriction clauses for scan (sans RestrictInfos) */
List *final_remote_exprs;
/* Bitmap of attr numbers we need to fetch from the remote server. */
Bitmapset *attrs_used;
/* True means that the query_pathkeys is safe to push down */
bool qp_is_pushdown_safe;
/* Cost and selectivity of local_conds. */
QualCost local_conds_cost;
Selectivity local_conds_sel;
/* Selectivity of join conditions */
Selectivity joinclause_sel;
/* Estimated size and cost for a scan, join, or grouping/aggregation. */
double rows;
int width;
Cost startup_cost;
Cost total_cost;
/*
* Estimated number of rows fetched from the foreign server, and costs
* excluding costs for transferring those rows from the foreign server.
* These are only used by estimate_path_cost_size().
*/
double retrieved_rows;
Cost rel_startup_cost;
Cost rel_total_cost;
/* Options extracted from catalogs. */
bool use_remote_estimate;
Cost fdw_startup_cost;
Cost fdw_tuple_cost;
List *shippable_extensions; /* OIDs of whitelisted extensions */
/* Cached catalog information. */
ForeignTable *table;
ForeignServer *server;
UserMapping *user; /* only set in use_remote_estimate mode */
int fetch_size; /* fetch size for this remote table */
/*
* Name of the relation while EXPLAINing ForeignScan. It is used for join
* relations but is set for all relations. For join relation, the name
* indicates which foreign tables are being joined and the join type used.
*/
StringInfo relation_name;
/* Join information */
RelOptInfo *outerrel;
RelOptInfo *innerrel;
JoinType jointype;
/* joinclauses contains only JOIN/ON conditions for an outer join */
List *joinclauses; /* List of RestrictInfo */
/* Upper relation information */
UpperRelationKind stage;
/* Grouping information */
List *grouped_tlist;
/* Subquery information */
bool make_outerrel_subquery; /* do we deparse outerrel as a
* subquery? */
bool make_innerrel_subquery; /* do we deparse innerrel as a
* subquery? */
Relids lower_subquery_rels; /* all relids appearing in lower
* subqueries */
/*
* Index of the relation. It is used to create an alias to a subquery
* representing the relation.
*/
int relation_index;
} PgFdwRelationInfo;
/* in postgres_fdw.c */
extern int set_transmission_modes(void);
extern void reset_transmission_modes(int nestlevel);
/* in connection.c */
extern PGconn *GetConnection(UserMapping *user, bool will_prep_stmt);
extern void ReleaseConnection(PGconn *conn);
extern unsigned int GetCursorNumber(PGconn *conn);
extern unsigned int GetPrepStmtNumber(PGconn *conn);
extern PGresult *pgfdw_get_result(PGconn *conn, const char *query);
extern PGresult *pgfdw_exec_query(PGconn *conn, const char *query);
extern void pgfdw_report_error(int elevel, PGresult *res, PGconn *conn,
bool clear, const char *sql);
/* in option.c */
extern int ExtractConnectionOptions(List *defelems,
const char **keywords,
const char **values);
extern List *ExtractExtensionList(const char *extensionsString,
bool warnOnMissing);
/* in deparse.c */
extern void classifyConditions(PlannerInfo *root,
RelOptInfo *baserel,
List *input_conds,
List **remote_conds,
List **local_conds);
extern bool is_foreign_expr(PlannerInfo *root,
RelOptInfo *baserel,
Expr *expr);
extern bool is_foreign_param(PlannerInfo *root,
RelOptInfo *baserel,
Expr *expr);
extern void deparseInsertSql(StringInfo buf, RangeTblEntry *rte,
Index rtindex, Relation rel,
List *targetAttrs, bool doNothing,
List *withCheckOptionList, List *returningList,
List **retrieved_attrs);
extern void deparseUpdateSql(StringInfo buf, RangeTblEntry *rte,
Index rtindex, Relation rel,
List *targetAttrs,
List *withCheckOptionList, List *returningList,
List **retrieved_attrs);
extern void deparseDirectUpdateSql(StringInfo buf, PlannerInfo *root,
Index rtindex, Relation rel,
RelOptInfo *foreignrel,
List *targetlist,
List *targetAttrs,
List *remote_conds,
List **params_list,
List *returningList,
List **retrieved_attrs);
extern void deparseDeleteSql(StringInfo buf, RangeTblEntry *rte,
Index rtindex, Relation rel,
List *returningList,
List **retrieved_attrs);
extern void deparseDirectDeleteSql(StringInfo buf, PlannerInfo *root,
Index rtindex, Relation rel,
RelOptInfo *foreignrel,
List *remote_conds,
List **params_list,
List *returningList,
List **retrieved_attrs);
extern void deparseAnalyzeSizeSql(StringInfo buf, Relation rel);
extern void deparseAnalyzeSql(StringInfo buf, Relation rel,
List **retrieved_attrs);
extern void deparseStringLiteral(StringInfo buf, const char *val);
extern Expr *find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel);
extern Expr *find_em_expr_for_input_target(PlannerInfo *root,
EquivalenceClass *ec,
PathTarget *target);
extern List *build_tlist_to_deparse(RelOptInfo *foreignrel);
extern void deparseSelectStmtForRel(StringInfo buf, PlannerInfo *root,
RelOptInfo *foreignrel, List *tlist,
List *remote_conds, List *pathkeys,
bool has_final_sort, bool has_limit,
bool is_subquery,
List **retrieved_attrs, List **params_list);
extern const char *get_jointype_name(JoinType jointype);
/* in shippable.c */
extern bool is_builtin(Oid objectId);
extern bool is_shippable(Oid objectId, Oid classId, PgFdwRelationInfo *fpinfo);
#endif /* POSTGRES_FDW_H */
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