LCOV - code coverage report
Current view: top level - contrib/auto_explain - auto_explain.c (source / functions) Hit Total Coverage
Test: PostgreSQL 18devel Lines: 92 103 89.3 %
Date: 2024-12-02 19:14:57 Functions: 6 6 100.0 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * auto_explain.c
       4             :  *
       5             :  *
       6             :  * Copyright (c) 2008-2024, PostgreSQL Global Development Group
       7             :  *
       8             :  * IDENTIFICATION
       9             :  *    contrib/auto_explain/auto_explain.c
      10             :  *
      11             :  *-------------------------------------------------------------------------
      12             :  */
      13             : #include "postgres.h"
      14             : 
      15             : #include <limits.h>
      16             : 
      17             : #include "access/parallel.h"
      18             : #include "commands/explain.h"
      19             : #include "common/pg_prng.h"
      20             : #include "executor/instrument.h"
      21             : #include "utils/guc.h"
      22             : 
      23          22 : PG_MODULE_MAGIC;
      24             : 
      25             : /* GUC variables */
      26             : static int  auto_explain_log_min_duration = -1; /* msec or -1 */
      27             : static int  auto_explain_log_parameter_max_length = -1; /* bytes or -1 */
      28             : static bool auto_explain_log_analyze = false;
      29             : static bool auto_explain_log_verbose = false;
      30             : static bool auto_explain_log_buffers = false;
      31             : static bool auto_explain_log_wal = false;
      32             : static bool auto_explain_log_triggers = false;
      33             : static bool auto_explain_log_timing = true;
      34             : static bool auto_explain_log_settings = false;
      35             : static int  auto_explain_log_format = EXPLAIN_FORMAT_TEXT;
      36             : static int  auto_explain_log_level = LOG;
      37             : static bool auto_explain_log_nested_statements = false;
      38             : static double auto_explain_sample_rate = 1;
      39             : 
      40             : static const struct config_enum_entry format_options[] = {
      41             :     {"text", EXPLAIN_FORMAT_TEXT, false},
      42             :     {"xml", EXPLAIN_FORMAT_XML, false},
      43             :     {"json", EXPLAIN_FORMAT_JSON, false},
      44             :     {"yaml", EXPLAIN_FORMAT_YAML, false},
      45             :     {NULL, 0, false}
      46             : };
      47             : 
      48             : static const struct config_enum_entry loglevel_options[] = {
      49             :     {"debug5", DEBUG5, false},
      50             :     {"debug4", DEBUG4, false},
      51             :     {"debug3", DEBUG3, false},
      52             :     {"debug2", DEBUG2, false},
      53             :     {"debug1", DEBUG1, false},
      54             :     {"debug", DEBUG2, true},
      55             :     {"info", INFO, false},
      56             :     {"notice", NOTICE, false},
      57             :     {"warning", WARNING, false},
      58             :     {"log", LOG, false},
      59             :     {NULL, 0, false}
      60             : };
      61             : 
      62             : /* Current nesting depth of ExecutorRun calls */
      63             : static int  nesting_level = 0;
      64             : 
      65             : /* Is the current top-level query to be sampled? */
      66             : static bool current_query_sampled = false;
      67             : 
      68             : #define auto_explain_enabled() \
      69             :     (auto_explain_log_min_duration >= 0 && \
      70             :      (nesting_level == 0 || auto_explain_log_nested_statements) && \
      71             :      current_query_sampled)
      72             : 
      73             : /* Saved hook values in case of unload */
      74             : static ExecutorStart_hook_type prev_ExecutorStart = NULL;
      75             : static ExecutorRun_hook_type prev_ExecutorRun = NULL;
      76             : static ExecutorFinish_hook_type prev_ExecutorFinish = NULL;
      77             : static ExecutorEnd_hook_type prev_ExecutorEnd = NULL;
      78             : 
      79             : static void explain_ExecutorStart(QueryDesc *queryDesc, int eflags);
      80             : static void explain_ExecutorRun(QueryDesc *queryDesc,
      81             :                                 ScanDirection direction,
      82             :                                 uint64 count, bool execute_once);
      83             : static void explain_ExecutorFinish(QueryDesc *queryDesc);
      84             : static void explain_ExecutorEnd(QueryDesc *queryDesc);
      85             : 
      86             : 
      87             : /*
      88             :  * Module load callback
      89             :  */
      90             : void
      91          22 : _PG_init(void)
      92             : {
      93             :     /* Define custom GUC variables. */
      94          22 :     DefineCustomIntVariable("auto_explain.log_min_duration",
      95             :                             "Sets the minimum execution time above which plans will be logged.",
      96             :                             "Zero prints all plans. -1 turns this feature off.",
      97             :                             &auto_explain_log_min_duration,
      98             :                             -1,
      99             :                             -1, INT_MAX,
     100             :                             PGC_SUSET,
     101             :                             GUC_UNIT_MS,
     102             :                             NULL,
     103             :                             NULL,
     104             :                             NULL);
     105             : 
     106          22 :     DefineCustomIntVariable("auto_explain.log_parameter_max_length",
     107             :                             "Sets the maximum length of query parameters to log.",
     108             :                             "Zero logs no query parameters, -1 logs them in full.",
     109             :                             &auto_explain_log_parameter_max_length,
     110             :                             -1,
     111             :                             -1, INT_MAX,
     112             :                             PGC_SUSET,
     113             :                             GUC_UNIT_BYTE,
     114             :                             NULL,
     115             :                             NULL,
     116             :                             NULL);
     117             : 
     118          22 :     DefineCustomBoolVariable("auto_explain.log_analyze",
     119             :                              "Use EXPLAIN ANALYZE for plan logging.",
     120             :                              NULL,
     121             :                              &auto_explain_log_analyze,
     122             :                              false,
     123             :                              PGC_SUSET,
     124             :                              0,
     125             :                              NULL,
     126             :                              NULL,
     127             :                              NULL);
     128             : 
     129          22 :     DefineCustomBoolVariable("auto_explain.log_settings",
     130             :                              "Log modified configuration parameters affecting query planning.",
     131             :                              NULL,
     132             :                              &auto_explain_log_settings,
     133             :                              false,
     134             :                              PGC_SUSET,
     135             :                              0,
     136             :                              NULL,
     137             :                              NULL,
     138             :                              NULL);
     139             : 
     140          22 :     DefineCustomBoolVariable("auto_explain.log_verbose",
     141             :                              "Use EXPLAIN VERBOSE for plan logging.",
     142             :                              NULL,
     143             :                              &auto_explain_log_verbose,
     144             :                              false,
     145             :                              PGC_SUSET,
     146             :                              0,
     147             :                              NULL,
     148             :                              NULL,
     149             :                              NULL);
     150             : 
     151          22 :     DefineCustomBoolVariable("auto_explain.log_buffers",
     152             :                              "Log buffers usage.",
     153             :                              NULL,
     154             :                              &auto_explain_log_buffers,
     155             :                              false,
     156             :                              PGC_SUSET,
     157             :                              0,
     158             :                              NULL,
     159             :                              NULL,
     160             :                              NULL);
     161             : 
     162          22 :     DefineCustomBoolVariable("auto_explain.log_wal",
     163             :                              "Log WAL usage.",
     164             :                              NULL,
     165             :                              &auto_explain_log_wal,
     166             :                              false,
     167             :                              PGC_SUSET,
     168             :                              0,
     169             :                              NULL,
     170             :                              NULL,
     171             :                              NULL);
     172             : 
     173          22 :     DefineCustomBoolVariable("auto_explain.log_triggers",
     174             :                              "Include trigger statistics in plans.",
     175             :                              "This has no effect unless log_analyze is also set.",
     176             :                              &auto_explain_log_triggers,
     177             :                              false,
     178             :                              PGC_SUSET,
     179             :                              0,
     180             :                              NULL,
     181             :                              NULL,
     182             :                              NULL);
     183             : 
     184          22 :     DefineCustomEnumVariable("auto_explain.log_format",
     185             :                              "EXPLAIN format to be used for plan logging.",
     186             :                              NULL,
     187             :                              &auto_explain_log_format,
     188             :                              EXPLAIN_FORMAT_TEXT,
     189             :                              format_options,
     190             :                              PGC_SUSET,
     191             :                              0,
     192             :                              NULL,
     193             :                              NULL,
     194             :                              NULL);
     195             : 
     196          22 :     DefineCustomEnumVariable("auto_explain.log_level",
     197             :                              "Log level for the plan.",
     198             :                              NULL,
     199             :                              &auto_explain_log_level,
     200             :                              LOG,
     201             :                              loglevel_options,
     202             :                              PGC_SUSET,
     203             :                              0,
     204             :                              NULL,
     205             :                              NULL,
     206             :                              NULL);
     207             : 
     208          22 :     DefineCustomBoolVariable("auto_explain.log_nested_statements",
     209             :                              "Log nested statements.",
     210             :                              NULL,
     211             :                              &auto_explain_log_nested_statements,
     212             :                              false,
     213             :                              PGC_SUSET,
     214             :                              0,
     215             :                              NULL,
     216             :                              NULL,
     217             :                              NULL);
     218             : 
     219          22 :     DefineCustomBoolVariable("auto_explain.log_timing",
     220             :                              "Collect timing data, not just row counts.",
     221             :                              NULL,
     222             :                              &auto_explain_log_timing,
     223             :                              true,
     224             :                              PGC_SUSET,
     225             :                              0,
     226             :                              NULL,
     227             :                              NULL,
     228             :                              NULL);
     229             : 
     230          22 :     DefineCustomRealVariable("auto_explain.sample_rate",
     231             :                              "Fraction of queries to process.",
     232             :                              NULL,
     233             :                              &auto_explain_sample_rate,
     234             :                              1.0,
     235             :                              0.0,
     236             :                              1.0,
     237             :                              PGC_SUSET,
     238             :                              0,
     239             :                              NULL,
     240             :                              NULL,
     241             :                              NULL);
     242             : 
     243          22 :     MarkGUCPrefixReserved("auto_explain");
     244             : 
     245             :     /* Install hooks. */
     246          22 :     prev_ExecutorStart = ExecutorStart_hook;
     247          22 :     ExecutorStart_hook = explain_ExecutorStart;
     248          22 :     prev_ExecutorRun = ExecutorRun_hook;
     249          22 :     ExecutorRun_hook = explain_ExecutorRun;
     250          22 :     prev_ExecutorFinish = ExecutorFinish_hook;
     251          22 :     ExecutorFinish_hook = explain_ExecutorFinish;
     252          22 :     prev_ExecutorEnd = ExecutorEnd_hook;
     253          22 :     ExecutorEnd_hook = explain_ExecutorEnd;
     254          22 : }
     255             : 
     256             : /*
     257             :  * ExecutorStart hook: start up logging if needed
     258             :  */
     259             : static void
     260          20 : explain_ExecutorStart(QueryDesc *queryDesc, int eflags)
     261             : {
     262             :     /*
     263             :      * At the beginning of each top-level statement, decide whether we'll
     264             :      * sample this statement.  If nested-statement explaining is enabled,
     265             :      * either all nested statements will be explained or none will.
     266             :      *
     267             :      * When in a parallel worker, we should do nothing, which we can implement
     268             :      * cheaply by pretending we decided not to sample the current statement.
     269             :      * If EXPLAIN is active in the parent session, data will be collected and
     270             :      * reported back to the parent, and it's no business of ours to interfere.
     271             :      */
     272          20 :     if (nesting_level == 0)
     273             :     {
     274          20 :         if (auto_explain_log_min_duration >= 0 && !IsParallelWorker())
     275          20 :             current_query_sampled = (pg_prng_double(&pg_global_prng_state) < auto_explain_sample_rate);
     276             :         else
     277           0 :             current_query_sampled = false;
     278             :     }
     279             : 
     280          20 :     if (auto_explain_enabled())
     281             :     {
     282             :         /* Enable per-node instrumentation iff log_analyze is required. */
     283          20 :         if (auto_explain_log_analyze && (eflags & EXEC_FLAG_EXPLAIN_ONLY) == 0)
     284             :         {
     285          20 :             if (auto_explain_log_timing)
     286          20 :                 queryDesc->instrument_options |= INSTRUMENT_TIMER;
     287             :             else
     288           0 :                 queryDesc->instrument_options |= INSTRUMENT_ROWS;
     289          20 :             if (auto_explain_log_buffers)
     290           0 :                 queryDesc->instrument_options |= INSTRUMENT_BUFFERS;
     291          20 :             if (auto_explain_log_wal)
     292           0 :                 queryDesc->instrument_options |= INSTRUMENT_WAL;
     293             :         }
     294             :     }
     295             : 
     296          20 :     if (prev_ExecutorStart)
     297           0 :         prev_ExecutorStart(queryDesc, eflags);
     298             :     else
     299          20 :         standard_ExecutorStart(queryDesc, eflags);
     300             : 
     301          20 :     if (auto_explain_enabled())
     302             :     {
     303             :         /*
     304             :          * Set up to track total elapsed time in ExecutorRun.  Make sure the
     305             :          * space is allocated in the per-query context so it will go away at
     306             :          * ExecutorEnd.
     307             :          */
     308          20 :         if (queryDesc->totaltime == NULL)
     309             :         {
     310             :             MemoryContext oldcxt;
     311             : 
     312          20 :             oldcxt = MemoryContextSwitchTo(queryDesc->estate->es_query_cxt);
     313          20 :             queryDesc->totaltime = InstrAlloc(1, INSTRUMENT_ALL, false);
     314          20 :             MemoryContextSwitchTo(oldcxt);
     315             :         }
     316             :     }
     317          20 : }
     318             : 
     319             : /*
     320             :  * ExecutorRun hook: all we need do is track nesting depth
     321             :  */
     322             : static void
     323          20 : explain_ExecutorRun(QueryDesc *queryDesc, ScanDirection direction,
     324             :                     uint64 count, bool execute_once)
     325             : {
     326          20 :     nesting_level++;
     327          20 :     PG_TRY();
     328             :     {
     329          20 :         if (prev_ExecutorRun)
     330           0 :             prev_ExecutorRun(queryDesc, direction, count, execute_once);
     331             :         else
     332          20 :             standard_ExecutorRun(queryDesc, direction, count, execute_once);
     333             :     }
     334           0 :     PG_FINALLY();
     335             :     {
     336          20 :         nesting_level--;
     337             :     }
     338          20 :     PG_END_TRY();
     339          20 : }
     340             : 
     341             : /*
     342             :  * ExecutorFinish hook: all we need do is track nesting depth
     343             :  */
     344             : static void
     345          20 : explain_ExecutorFinish(QueryDesc *queryDesc)
     346             : {
     347          20 :     nesting_level++;
     348          20 :     PG_TRY();
     349             :     {
     350          20 :         if (prev_ExecutorFinish)
     351           0 :             prev_ExecutorFinish(queryDesc);
     352             :         else
     353          20 :             standard_ExecutorFinish(queryDesc);
     354             :     }
     355           0 :     PG_FINALLY();
     356             :     {
     357          20 :         nesting_level--;
     358             :     }
     359          20 :     PG_END_TRY();
     360          20 : }
     361             : 
     362             : /*
     363             :  * ExecutorEnd hook: log results if needed
     364             :  */
     365             : static void
     366          20 : explain_ExecutorEnd(QueryDesc *queryDesc)
     367             : {
     368          20 :     if (queryDesc->totaltime && auto_explain_enabled())
     369             :     {
     370             :         MemoryContext oldcxt;
     371             :         double      msec;
     372             : 
     373             :         /*
     374             :          * Make sure we operate in the per-query context, so any cruft will be
     375             :          * discarded later during ExecutorEnd.
     376             :          */
     377          20 :         oldcxt = MemoryContextSwitchTo(queryDesc->estate->es_query_cxt);
     378             : 
     379             :         /*
     380             :          * Make sure stats accumulation is done.  (Note: it's okay if several
     381             :          * levels of hook all do this.)
     382             :          */
     383          20 :         InstrEndLoop(queryDesc->totaltime);
     384             : 
     385             :         /* Log plan if duration is exceeded. */
     386          20 :         msec = queryDesc->totaltime->total * 1000.0;
     387          20 :         if (msec >= auto_explain_log_min_duration)
     388             :         {
     389          20 :             ExplainState *es = NewExplainState();
     390             : 
     391          20 :             es->analyze = (queryDesc->instrument_options && auto_explain_log_analyze);
     392          20 :             es->verbose = auto_explain_log_verbose;
     393          20 :             es->buffers = (es->analyze && auto_explain_log_buffers);
     394          20 :             es->wal = (es->analyze && auto_explain_log_wal);
     395          20 :             es->timing = (es->analyze && auto_explain_log_timing);
     396          20 :             es->summary = es->analyze;
     397             :             /* No support for MEMORY */
     398             :             /* es->memory = false; */
     399          20 :             es->format = auto_explain_log_format;
     400          20 :             es->settings = auto_explain_log_settings;
     401             : 
     402          20 :             ExplainBeginOutput(es);
     403          20 :             ExplainQueryText(es, queryDesc);
     404          20 :             ExplainQueryParameters(es, queryDesc->params, auto_explain_log_parameter_max_length);
     405          20 :             ExplainPrintPlan(es, queryDesc);
     406          20 :             if (es->analyze && auto_explain_log_triggers)
     407           0 :                 ExplainPrintTriggers(es, queryDesc);
     408          20 :             if (es->costs)
     409          20 :                 ExplainPrintJITSummary(es, queryDesc);
     410          20 :             ExplainEndOutput(es);
     411             : 
     412             :             /* Remove last line break */
     413          20 :             if (es->str->len > 0 && es->str->data[es->str->len - 1] == '\n')
     414          14 :                 es->str->data[--es->str->len] = '\0';
     415             : 
     416             :             /* Fix JSON to output an object */
     417          20 :             if (auto_explain_log_format == EXPLAIN_FORMAT_JSON)
     418             :             {
     419           6 :                 es->str->data[0] = '{';
     420           6 :                 es->str->data[es->str->len - 1] = '}';
     421             :             }
     422             : 
     423             :             /*
     424             :              * Note: we rely on the existing logging of context or
     425             :              * debug_query_string to identify just which statement is being
     426             :              * reported.  This isn't ideal but trying to do it here would
     427             :              * often result in duplication.
     428             :              */
     429          20 :             ereport(auto_explain_log_level,
     430             :                     (errmsg("duration: %.3f ms  plan:\n%s",
     431             :                             msec, es->str->data),
     432             :                      errhidestmt(true)));
     433             :         }
     434             : 
     435          20 :         MemoryContextSwitchTo(oldcxt);
     436             :     }
     437             : 
     438          20 :     if (prev_ExecutorEnd)
     439           0 :         prev_ExecutorEnd(queryDesc);
     440             :     else
     441          20 :         standard_ExecutorEnd(queryDesc);
     442          20 : }

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