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This commit adds a new option WAL similar to existing option BUFFERS in the
EXPLAIN command. This option allows to include information on WAL record
generation added by commit df3b181499
in EXPLAIN output.
This also allows the WAL usage information to be displayed via
the auto_explain module. A new parameter auto_explain.log_wal controls
whether WAL usage statistics are printed when an execution plan is logged.
This parameter has no effect unless auto_explain.log_analyze is enabled.
Author: Julien Rouhaud
Reviewed-by: Dilip Kumar and Amit Kapila
Discussion: https://postgr.es/m/CAB-hujrP8ZfUkvL5OYETipQwA=e3n7oqHFU=4ZLxWS_Cza3kQQ@mail.gmail.com
437 lines
11 KiB
C
437 lines
11 KiB
C
/*-------------------------------------------------------------------------
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*
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* auto_explain.c
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*
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*
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* Copyright (c) 2008-2020, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* contrib/auto_explain/auto_explain.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include <limits.h>
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#include "access/parallel.h"
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#include "commands/explain.h"
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#include "executor/instrument.h"
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#include "jit/jit.h"
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#include "utils/guc.h"
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PG_MODULE_MAGIC;
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/* GUC variables */
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static int auto_explain_log_min_duration = -1; /* msec or -1 */
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static bool auto_explain_log_analyze = false;
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static bool auto_explain_log_verbose = false;
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static bool auto_explain_log_buffers = false;
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static bool auto_explain_log_wal = false;
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static bool auto_explain_log_triggers = false;
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static bool auto_explain_log_timing = true;
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static bool auto_explain_log_settings = false;
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static int auto_explain_log_format = EXPLAIN_FORMAT_TEXT;
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static int auto_explain_log_level = LOG;
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static bool auto_explain_log_nested_statements = false;
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static double auto_explain_sample_rate = 1;
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static const struct config_enum_entry format_options[] = {
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{"text", EXPLAIN_FORMAT_TEXT, false},
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{"xml", EXPLAIN_FORMAT_XML, false},
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{"json", EXPLAIN_FORMAT_JSON, false},
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{"yaml", EXPLAIN_FORMAT_YAML, false},
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{NULL, 0, false}
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};
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static const struct config_enum_entry loglevel_options[] = {
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{"debug5", DEBUG5, false},
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{"debug4", DEBUG4, false},
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{"debug3", DEBUG3, false},
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{"debug2", DEBUG2, false},
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{"debug1", DEBUG1, false},
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{"debug", DEBUG2, true},
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{"info", INFO, false},
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{"notice", NOTICE, false},
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{"warning", WARNING, false},
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{"log", LOG, false},
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{NULL, 0, false}
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};
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/* Current nesting depth of ExecutorRun calls */
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static int nesting_level = 0;
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/* Is the current top-level query to be sampled? */
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static bool current_query_sampled = false;
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#define auto_explain_enabled() \
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(auto_explain_log_min_duration >= 0 && \
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(nesting_level == 0 || auto_explain_log_nested_statements) && \
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current_query_sampled)
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/* Saved hook values in case of unload */
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static ExecutorStart_hook_type prev_ExecutorStart = NULL;
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static ExecutorRun_hook_type prev_ExecutorRun = NULL;
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static ExecutorFinish_hook_type prev_ExecutorFinish = NULL;
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static ExecutorEnd_hook_type prev_ExecutorEnd = NULL;
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void _PG_init(void);
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void _PG_fini(void);
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static void explain_ExecutorStart(QueryDesc *queryDesc, int eflags);
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static void explain_ExecutorRun(QueryDesc *queryDesc,
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ScanDirection direction,
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uint64 count, bool execute_once);
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static void explain_ExecutorFinish(QueryDesc *queryDesc);
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static void explain_ExecutorEnd(QueryDesc *queryDesc);
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/*
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* Module load callback
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*/
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void
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_PG_init(void)
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{
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/* Define custom GUC variables. */
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DefineCustomIntVariable("auto_explain.log_min_duration",
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"Sets the minimum execution time above which plans will be logged.",
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"Zero prints all plans. -1 turns this feature off.",
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&auto_explain_log_min_duration,
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-1,
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-1, INT_MAX,
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PGC_SUSET,
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GUC_UNIT_MS,
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NULL,
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NULL,
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NULL);
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DefineCustomBoolVariable("auto_explain.log_analyze",
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"Use EXPLAIN ANALYZE for plan logging.",
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NULL,
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&auto_explain_log_analyze,
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false,
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PGC_SUSET,
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0,
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NULL,
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NULL,
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NULL);
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DefineCustomBoolVariable("auto_explain.log_settings",
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"Log modified configuration parameters affecting query planning.",
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NULL,
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&auto_explain_log_settings,
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false,
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PGC_SUSET,
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0,
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NULL,
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NULL,
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NULL);
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DefineCustomBoolVariable("auto_explain.log_verbose",
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"Use EXPLAIN VERBOSE for plan logging.",
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NULL,
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&auto_explain_log_verbose,
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false,
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PGC_SUSET,
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0,
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NULL,
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NULL,
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NULL);
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DefineCustomBoolVariable("auto_explain.log_buffers",
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"Log buffers usage.",
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NULL,
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&auto_explain_log_buffers,
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false,
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PGC_SUSET,
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0,
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NULL,
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NULL,
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NULL);
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DefineCustomBoolVariable("auto_explain.log_wal",
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"Log WAL usage.",
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NULL,
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&auto_explain_log_wal,
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false,
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PGC_SUSET,
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0,
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NULL,
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NULL,
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NULL);
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DefineCustomBoolVariable("auto_explain.log_triggers",
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"Include trigger statistics in plans.",
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"This has no effect unless log_analyze is also set.",
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&auto_explain_log_triggers,
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false,
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PGC_SUSET,
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0,
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NULL,
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NULL,
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NULL);
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DefineCustomEnumVariable("auto_explain.log_format",
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"EXPLAIN format to be used for plan logging.",
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NULL,
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&auto_explain_log_format,
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EXPLAIN_FORMAT_TEXT,
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format_options,
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PGC_SUSET,
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0,
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NULL,
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NULL,
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NULL);
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DefineCustomEnumVariable("auto_explain.log_level",
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"Log level for the plan.",
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NULL,
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&auto_explain_log_level,
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LOG,
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loglevel_options,
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PGC_SUSET,
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0,
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NULL,
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NULL,
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NULL);
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DefineCustomBoolVariable("auto_explain.log_nested_statements",
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"Log nested statements.",
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NULL,
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&auto_explain_log_nested_statements,
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false,
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PGC_SUSET,
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0,
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NULL,
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NULL,
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NULL);
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DefineCustomBoolVariable("auto_explain.log_timing",
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"Collect timing data, not just row counts.",
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NULL,
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&auto_explain_log_timing,
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true,
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PGC_SUSET,
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0,
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NULL,
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NULL,
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NULL);
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DefineCustomRealVariable("auto_explain.sample_rate",
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"Fraction of queries to process.",
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NULL,
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&auto_explain_sample_rate,
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1.0,
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0.0,
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1.0,
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PGC_SUSET,
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0,
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NULL,
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NULL,
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NULL);
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EmitWarningsOnPlaceholders("auto_explain");
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/* Install hooks. */
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prev_ExecutorStart = ExecutorStart_hook;
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ExecutorStart_hook = explain_ExecutorStart;
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prev_ExecutorRun = ExecutorRun_hook;
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ExecutorRun_hook = explain_ExecutorRun;
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prev_ExecutorFinish = ExecutorFinish_hook;
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ExecutorFinish_hook = explain_ExecutorFinish;
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prev_ExecutorEnd = ExecutorEnd_hook;
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ExecutorEnd_hook = explain_ExecutorEnd;
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}
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/*
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* Module unload callback
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*/
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void
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_PG_fini(void)
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{
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/* Uninstall hooks. */
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ExecutorStart_hook = prev_ExecutorStart;
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ExecutorRun_hook = prev_ExecutorRun;
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ExecutorFinish_hook = prev_ExecutorFinish;
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ExecutorEnd_hook = prev_ExecutorEnd;
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}
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/*
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* ExecutorStart hook: start up logging if needed
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*/
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static void
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explain_ExecutorStart(QueryDesc *queryDesc, int eflags)
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{
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/*
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* At the beginning of each top-level statement, decide whether we'll
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* sample this statement. If nested-statement explaining is enabled,
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* either all nested statements will be explained or none will.
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*
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* When in a parallel worker, we should do nothing, which we can implement
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* cheaply by pretending we decided not to sample the current statement.
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* If EXPLAIN is active in the parent session, data will be collected and
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* reported back to the parent, and it's no business of ours to interfere.
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*/
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if (nesting_level == 0)
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{
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if (auto_explain_log_min_duration >= 0 && !IsParallelWorker())
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current_query_sampled = (random() < auto_explain_sample_rate *
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((double) MAX_RANDOM_VALUE + 1));
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else
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current_query_sampled = false;
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}
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if (auto_explain_enabled())
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{
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/* Enable per-node instrumentation iff log_analyze is required. */
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if (auto_explain_log_analyze && (eflags & EXEC_FLAG_EXPLAIN_ONLY) == 0)
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{
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if (auto_explain_log_timing)
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queryDesc->instrument_options |= INSTRUMENT_TIMER;
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else
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queryDesc->instrument_options |= INSTRUMENT_ROWS;
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if (auto_explain_log_buffers)
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queryDesc->instrument_options |= INSTRUMENT_BUFFERS;
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if (auto_explain_log_wal)
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queryDesc->instrument_options |= INSTRUMENT_WAL;
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}
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}
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if (prev_ExecutorStart)
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prev_ExecutorStart(queryDesc, eflags);
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else
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standard_ExecutorStart(queryDesc, eflags);
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if (auto_explain_enabled())
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{
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/*
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* Set up to track total elapsed time in ExecutorRun. Make sure the
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* space is allocated in the per-query context so it will go away at
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* ExecutorEnd.
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*/
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if (queryDesc->totaltime == NULL)
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{
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MemoryContext oldcxt;
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oldcxt = MemoryContextSwitchTo(queryDesc->estate->es_query_cxt);
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queryDesc->totaltime = InstrAlloc(1, INSTRUMENT_ALL);
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MemoryContextSwitchTo(oldcxt);
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}
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}
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}
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/*
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* ExecutorRun hook: all we need do is track nesting depth
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*/
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static void
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explain_ExecutorRun(QueryDesc *queryDesc, ScanDirection direction,
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uint64 count, bool execute_once)
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{
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nesting_level++;
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PG_TRY();
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{
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if (prev_ExecutorRun)
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prev_ExecutorRun(queryDesc, direction, count, execute_once);
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else
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standard_ExecutorRun(queryDesc, direction, count, execute_once);
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}
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PG_FINALLY();
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{
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nesting_level--;
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}
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PG_END_TRY();
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}
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/*
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* ExecutorFinish hook: all we need do is track nesting depth
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*/
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static void
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explain_ExecutorFinish(QueryDesc *queryDesc)
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{
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nesting_level++;
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PG_TRY();
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{
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if (prev_ExecutorFinish)
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prev_ExecutorFinish(queryDesc);
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else
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standard_ExecutorFinish(queryDesc);
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}
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PG_FINALLY();
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{
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nesting_level--;
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}
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PG_END_TRY();
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}
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/*
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* ExecutorEnd hook: log results if needed
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*/
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static void
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explain_ExecutorEnd(QueryDesc *queryDesc)
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{
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if (queryDesc->totaltime && auto_explain_enabled())
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{
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double msec;
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/*
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* Make sure stats accumulation is done. (Note: it's okay if several
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* levels of hook all do this.)
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*/
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InstrEndLoop(queryDesc->totaltime);
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/* Log plan if duration is exceeded. */
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msec = queryDesc->totaltime->total * 1000.0;
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if (msec >= auto_explain_log_min_duration)
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{
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ExplainState *es = NewExplainState();
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es->analyze = (queryDesc->instrument_options && auto_explain_log_analyze);
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es->verbose = auto_explain_log_verbose;
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es->buffers = (es->analyze && auto_explain_log_buffers);
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es->wal = (es->analyze && auto_explain_log_wal);
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es->timing = (es->analyze && auto_explain_log_timing);
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es->summary = es->analyze;
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es->format = auto_explain_log_format;
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es->settings = auto_explain_log_settings;
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ExplainBeginOutput(es);
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ExplainQueryText(es, queryDesc);
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ExplainPrintPlan(es, queryDesc);
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if (es->analyze && auto_explain_log_triggers)
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ExplainPrintTriggers(es, queryDesc);
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if (es->costs)
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ExplainPrintJITSummary(es, queryDesc);
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ExplainEndOutput(es);
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/* Remove last line break */
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if (es->str->len > 0 && es->str->data[es->str->len - 1] == '\n')
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es->str->data[--es->str->len] = '\0';
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/* Fix JSON to output an object */
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if (auto_explain_log_format == EXPLAIN_FORMAT_JSON)
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{
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es->str->data[0] = '{';
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es->str->data[es->str->len - 1] = '}';
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}
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/*
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* Note: we rely on the existing logging of context or
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* debug_query_string to identify just which statement is being
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* reported. This isn't ideal but trying to do it here would
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* often result in duplication.
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*/
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ereport(auto_explain_log_level,
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(errmsg("duration: %.3f ms plan:\n%s",
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msec, es->str->data),
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errhidestmt(true)));
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pfree(es->str->data);
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}
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}
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if (prev_ExecutorEnd)
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prev_ExecutorEnd(queryDesc);
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else
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standard_ExecutorEnd(queryDesc);
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}
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