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As of 9.3, ruleutils.c goes to some lengths to ensure that table and column aliases used in its output are unique. Of course this takes more time than was required before, which in itself isn't fatal. However, EXPLAIN was set up so that recalculation of the unique aliases was repeated for each subexpression printed in a plan. That results in O(N^2) time and memory consumption for large plan trees, which did not happen in older branches. Fortunately, the expensive work is the same across a whole plan tree, so there is no need to repeat it; we can do most of the initialization just once per query and re-use it for each subexpression. This buys back most (not all) of the performance loss since 9.2. We need an extra ExplainState field to hold the precalculated deparse context. That's no problem in HEAD, but in the back branches, expanding sizeof(ExplainState) seems risky because third-party extensions might have local variables of that struct type. So, in 9.4 and 9.3, introduce an auxiliary struct to keep sizeof(ExplainState) the same. We should refactor the APIs to avoid such local variables in future, but that's material for a separate HEAD-only commit. Per gripe from Alexey Bashtanov. Back-patch to 9.3 where the issue was introduced.
99 lines
3.3 KiB
C
99 lines
3.3 KiB
C
/*-------------------------------------------------------------------------
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*
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* explain.h
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* prototypes for explain.c
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*
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* Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994-5, Regents of the University of California
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*
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* src/include/commands/explain.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef EXPLAIN_H
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#define EXPLAIN_H
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#include "executor/executor.h"
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#include "lib/stringinfo.h"
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typedef enum ExplainFormat
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{
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EXPLAIN_FORMAT_TEXT,
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EXPLAIN_FORMAT_XML,
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EXPLAIN_FORMAT_JSON,
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EXPLAIN_FORMAT_YAML
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} ExplainFormat;
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/* Crude hack to avoid changing sizeof(ExplainState) in released branches */
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typedef struct ExplainStateExtra
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{
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List *groupingstack; /* format-specific grouping state */
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List *deparsecxt; /* context list for deparsing expressions */
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} ExplainStateExtra;
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typedef struct ExplainState
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{
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StringInfo str; /* output buffer */
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/* options */
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bool verbose; /* be verbose */
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bool analyze; /* print actual times */
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bool costs; /* print costs */
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bool buffers; /* print buffer usage */
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bool timing; /* print timing */
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ExplainFormat format; /* output format */
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/* other states */
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PlannedStmt *pstmt; /* top of plan */
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List *rtable; /* range table */
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List *rtable_names; /* alias names for RTEs */
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int indent; /* current indentation level */
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ExplainStateExtra *extra; /* pointer to additional data */
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} ExplainState;
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/* Hook for plugins to get control in ExplainOneQuery() */
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typedef void (*ExplainOneQuery_hook_type) (Query *query,
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IntoClause *into,
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ExplainState *es,
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const char *queryString,
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ParamListInfo params);
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extern PGDLLIMPORT ExplainOneQuery_hook_type ExplainOneQuery_hook;
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/* Hook for plugins to get control in explain_get_index_name() */
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typedef const char *(*explain_get_index_name_hook_type) (Oid indexId);
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extern PGDLLIMPORT explain_get_index_name_hook_type explain_get_index_name_hook;
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extern void ExplainQuery(ExplainStmt *stmt, const char *queryString,
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ParamListInfo params, DestReceiver *dest);
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extern void ExplainInitState(ExplainState *es);
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extern TupleDesc ExplainResultDesc(ExplainStmt *stmt);
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extern void ExplainOneUtility(Node *utilityStmt, IntoClause *into,
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ExplainState *es,
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const char *queryString, ParamListInfo params);
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extern void ExplainOnePlan(PlannedStmt *plannedstmt, IntoClause *into,
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ExplainState *es,
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const char *queryString, ParamListInfo params);
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extern void ExplainPrintPlan(ExplainState *es, QueryDesc *queryDesc);
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extern void ExplainQueryText(ExplainState *es, QueryDesc *queryDesc);
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extern void ExplainBeginOutput(ExplainState *es);
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extern void ExplainEndOutput(ExplainState *es);
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extern void ExplainSeparatePlans(ExplainState *es);
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extern void ExplainPropertyList(const char *qlabel, List *data,
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ExplainState *es);
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extern void ExplainPropertyText(const char *qlabel, const char *value,
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ExplainState *es);
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extern void ExplainPropertyInteger(const char *qlabel, int value,
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ExplainState *es);
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extern void ExplainPropertyLong(const char *qlabel, long value,
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ExplainState *es);
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extern void ExplainPropertyFloat(const char *qlabel, double value, int ndigits,
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ExplainState *es);
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#endif /* EXPLAIN_H */
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