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1<?xml version="1.0" encoding="UTF-8" standalone="no"?>2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>F.32. pg_stat_statements — track statistics of SQL planning and execution</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="pgrowlocks.html" title="F.31. pgrowlocks — show a table's row locking information" /><link rel="next" href="pgstattuple.html" title="F.33. pgstattuple — obtain tuple-level statistics" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">F.32. pg_stat_statements — track statistics of SQL planning and execution</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="pgrowlocks.html" title="F.31. pgrowlocks — show a table's row locking information">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="contrib.html" title="Appendix F. Additional Supplied Modules and Extensions">Up</a></td><th width="60%" align="center">Appendix F. Additional Supplied Modules and Extensions</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="pgstattuple.html" title="F.33. pgstattuple — obtain tuple-level statistics">Next</a></td></tr></table><hr /></div><div class="sect1" id="PGSTATSTATEMENTS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">F.32. pg_stat_statements — track statistics of SQL planning and execution <a href="#PGSTATSTATEMENTS" class="id_link">#</a></h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="pgstatstatements.html#PGSTATSTATEMENTS-PG-STAT-STATEMENTS">F.32.1. The <code class="structname">pg_stat_statements</code> View</a></span></dt><dt><span class="sect2"><a href="pgstatstatements.html#PGSTATSTATEMENTS-PG-STAT-STATEMENTS-INFO">F.32.2. The <code class="structname">pg_stat_statements_info</code> View</a></span></dt><dt><span class="sect2"><a href="pgstatstatements.html#PGSTATSTATEMENTS-FUNCS">F.32.3. Functions</a></span></dt><dt><span class="sect2"><a href="pgstatstatements.html#PGSTATSTATEMENTS-CONFIG-PARAMS">F.32.4. Configuration Parameters</a></span></dt><dt><span class="sect2"><a href="pgstatstatements.html#PGSTATSTATEMENTS-SAMPLE-OUTPUT">F.32.5. Sample Output</a></span></dt><dt><span class="sect2"><a href="pgstatstatements.html#PGSTATSTATEMENTS-AUTHORS">F.32.6. Authors</a></span></dt></dl></div><a id="id-1.11.7.42.2" class="indexterm"></a><p>3 The <code class="filename">pg_stat_statements</code> module provides a means for4 tracking planning and execution statistics of all SQL statements executed by5 a server.6 </p><p>7 The module must be loaded by adding <code class="literal">pg_stat_statements</code> to8 <a class="xref" href="runtime-config-client.html#GUC-SHARED-PRELOAD-LIBRARIES">shared_preload_libraries</a> in9 <code class="filename">postgresql.conf</code>, because it requires additional shared memory.10 This means that a server restart is needed to add or remove the module.11 In addition, query identifier calculation must be enabled in order for the12 module to be active, which is done automatically if <a class="xref" href="runtime-config-statistics.html#GUC-COMPUTE-QUERY-ID">compute_query_id</a>13 is set to <code class="literal">auto</code> or <code class="literal">on</code>, or any third-party14 module that calculates query identifiers is loaded.15 </p><p>16 When <code class="filename">pg_stat_statements</code> is active, it tracks17 statistics across all databases of the server. To access and manipulate18 these statistics, the module provides views19 <code class="structname">pg_stat_statements</code> and20 <code class="structname">pg_stat_statements_info</code>,21 and the utility functions <code class="function">pg_stat_statements_reset</code> and22 <code class="function">pg_stat_statements</code>. These are not available globally but23 can be enabled for a specific database with24 <code class="command">CREATE EXTENSION pg_stat_statements</code>.25 </p><div class="sect2" id="PGSTATSTATEMENTS-PG-STAT-STATEMENTS"><div class="titlepage"><div><div><h3 class="title">F.32.1. The <code class="structname">pg_stat_statements</code> View <a href="#PGSTATSTATEMENTS-PG-STAT-STATEMENTS" class="id_link">#</a></h3></div></div></div><p>26 The statistics gathered by the module are made available via a27 view named <code class="structname">pg_stat_statements</code>. This view28 contains one row for each distinct combination of database ID, user29 ID, query ID and whether it's a top-level statement or not (up to30 the maximum number of distinct statements that the module can track).31 The columns of the view are shown in32 <a class="xref" href="pgstatstatements.html#PGSTATSTATEMENTS-COLUMNS" title="Table F.22. pg_stat_statements Columns">Table F.22</a>.33 </p><div class="table" id="PGSTATSTATEMENTS-COLUMNS"><p class="title"><strong>Table F.22. <code class="structname">pg_stat_statements</code> Columns</strong></p><div class="table-contents"><table class="table" summary="pg_stat_statements Columns" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">34 Column Type35 </p>36 <p>37 Description38 </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">39 <code class="structfield">userid</code> <code class="type">oid</code>40 (references <a class="link" href="catalog-pg-authid.html" title="53.8. pg_authid"><code class="structname">pg_authid</code></a>.<code class="structfield">oid</code>)41 </p>42 <p>43 OID of user who executed the statement44 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">45 <code class="structfield">dbid</code> <code class="type">oid</code>46 (references <a class="link" href="catalog-pg-database.html" title="53.15. pg_database"><code class="structname">pg_database</code></a>.<code class="structfield">oid</code>)47 </p>48 <p>49 OID of database in which the statement was executed50 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">51 <code class="structfield">toplevel</code> <code class="type">bool</code>52 </p>53 <p>54 True if the query was executed as a top-level statement55 (always true if <code class="varname">pg_stat_statements.track</code> is set to56 <code class="literal">top</code>)57 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">58 <code class="structfield">queryid</code> <code class="type">bigint</code>59 </p>60 <p>61 Hash code to identify identical normalized queries.62 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">63 <code class="structfield">query</code> <code class="type">text</code>64 </p>65 <p>66 Text of a representative statement67 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">68 <code class="structfield">plans</code> <code class="type">bigint</code>69 </p>70 <p>71 Number of times the statement was planned72 (if <code class="varname">pg_stat_statements.track_planning</code> is enabled,73 otherwise zero)74 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">75 <code class="structfield">total_plan_time</code> <code class="type">double precision</code>76 </p>77 <p>78 Total time spent planning the statement, in milliseconds79 (if <code class="varname">pg_stat_statements.track_planning</code> is enabled,80 otherwise zero)81 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">82 <code class="structfield">min_plan_time</code> <code class="type">double precision</code>83 </p>84 <p>85 Minimum time spent planning the statement, in milliseconds86 (if <code class="varname">pg_stat_statements.track_planning</code> is enabled,87 otherwise zero)88 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">89 <code class="structfield">max_plan_time</code> <code class="type">double precision</code>90 </p>91 <p>92 Maximum time spent planning the statement, in milliseconds93 (if <code class="varname">pg_stat_statements.track_planning</code> is enabled,94 otherwise zero)95 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">96 <code class="structfield">mean_plan_time</code> <code class="type">double precision</code>97 </p>98 <p>99 Mean time spent planning the statement, in milliseconds100 (if <code class="varname">pg_stat_statements.track_planning</code> is enabled,101 otherwise zero)102 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">103 <code class="structfield">stddev_plan_time</code> <code class="type">double precision</code>104 </p>105 <p>106 Population standard deviation of time spent planning the statement,107 in milliseconds108 (if <code class="varname">pg_stat_statements.track_planning</code> is enabled,109 otherwise zero)110 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">111 <code class="structfield">calls</code> <code class="type">bigint</code>112 </p>113 <p>114 Number of times the statement was executed115 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">116 <code class="structfield">total_exec_time</code> <code class="type">double precision</code>117 </p>118 <p>119 Total time spent executing the statement, in milliseconds120 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">121 <code class="structfield">min_exec_time</code> <code class="type">double precision</code>122 </p>123 <p>124 Minimum time spent executing the statement, in milliseconds125 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">126 <code class="structfield">max_exec_time</code> <code class="type">double precision</code>127 </p>128 <p>129 Maximum time spent executing the statement, in milliseconds130 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">131 <code class="structfield">mean_exec_time</code> <code class="type">double precision</code>132 </p>133 <p>134 Mean time spent executing the statement, in milliseconds135 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">136 <code class="structfield">stddev_exec_time</code> <code class="type">double precision</code>137 </p>138 <p>139 Population standard deviation of time spent executing the statement, in milliseconds140 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">141 <code class="structfield">rows</code> <code class="type">bigint</code>142 </p>143 <p>144 Total number of rows retrieved or affected by the statement145 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">146 <code class="structfield">shared_blks_hit</code> <code class="type">bigint</code>147 </p>148 <p>149 Total number of shared block cache hits by the statement150 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">151 <code class="structfield">shared_blks_read</code> <code class="type">bigint</code>152 </p>153 <p>154 Total number of shared blocks read by the statement155 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">156 <code class="structfield">shared_blks_dirtied</code> <code class="type">bigint</code>157 </p>158 <p>159 Total number of shared blocks dirtied by the statement160 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">161 <code class="structfield">shared_blks_written</code> <code class="type">bigint</code>162 </p>163 <p>164 Total number of shared blocks written by the statement165 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">166 <code class="structfield">local_blks_hit</code> <code class="type">bigint</code>167 </p>168 <p>169 Total number of local block cache hits by the statement170 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">171 <code class="structfield">local_blks_read</code> <code class="type">bigint</code>172 </p>173 <p>174 Total number of local blocks read by the statement175 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">176 <code class="structfield">local_blks_dirtied</code> <code class="type">bigint</code>177 </p>178 <p>179 Total number of local blocks dirtied by the statement180 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">181 <code class="structfield">local_blks_written</code> <code class="type">bigint</code>182 </p>183 <p>184 Total number of local blocks written by the statement185 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">186 <code class="structfield">temp_blks_read</code> <code class="type">bigint</code>187 </p>188 <p>189 Total number of temp blocks read by the statement190 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">191 <code class="structfield">temp_blks_written</code> <code class="type">bigint</code>192 </p>193 <p>194 Total number of temp blocks written by the statement195 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">196 <code class="structfield">blk_read_time</code> <code class="type">double precision</code>197 </p>198 <p>199 Total time the statement spent reading data file blocks, in milliseconds200 (if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> is enabled, otherwise zero)201 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">202 <code class="structfield">blk_write_time</code> <code class="type">double precision</code>203 </p>204 <p>205 Total time the statement spent writing data file blocks, in milliseconds206 (if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> is enabled, otherwise zero)207 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">208 <code class="structfield">temp_blk_read_time</code> <code class="type">double precision</code>209 </p>210 <p>211 Total time the statement spent reading temporary file blocks, in212 milliseconds (if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> is enabled,213 otherwise zero)214 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">215 <code class="structfield">temp_blk_write_time</code> <code class="type">double precision</code>216 </p>217 <p>218 Total time the statement spent writing temporary file blocks, in219 milliseconds (if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> is enabled,220 otherwise zero)221 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">222 <code class="structfield">wal_records</code> <code class="type">bigint</code>223 </p>224 <p>225 Total number of WAL records generated by the statement226 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">227 <code class="structfield">wal_fpi</code> <code class="type">bigint</code>228 </p>229 <p>230 Total number of WAL full page images generated by the statement231 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">232 <code class="structfield">wal_bytes</code> <code class="type">numeric</code>233 </p>234 <p>235 Total amount of WAL generated by the statement in bytes236 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">237 <code class="structfield">jit_functions</code> <code class="type">bigint</code>238 </p>239 <p>240 Total number of functions JIT-compiled by the statement241 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">242 <code class="structfield">jit_generation_time</code> <code class="type">double precision</code>243 </p>244 <p>245 Total time spent by the statement on generating JIT code, in milliseconds246 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">247 <code class="structfield">jit_inlining_count</code> <code class="type">bigint</code>248 </p>249 <p>250 Number of times functions have been inlined251 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">252 <code class="structfield">jit_inlining_time</code> <code class="type">double precision</code>253 </p>254 <p>255 Total time spent by the statement on inlining functions, in milliseconds256 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">257 <code class="structfield">jit_optimization_count</code> <code class="type">bigint</code>258 </p>259 <p>260 Number of times the statement has been optimized261 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">262 <code class="structfield">jit_optimization_time</code> <code class="type">double precision</code>263 </p>264 <p>265 Total time spent by the statement on optimizing, in milliseconds266 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">267 <code class="structfield">jit_emission_count</code> <code class="type">bigint</code>268 </p>269 <p>270 Number of times code has been emitted271 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">272 <code class="structfield">jit_emission_time</code> <code class="type">double precision</code>273 </p>274 <p>275 Total time spent by the statement on emitting code, in milliseconds276 </p></td></tr></tbody></table></div></div><br class="table-break" /><p>277 For security reasons, only superusers and roles with privileges of the278 <code class="literal">pg_read_all_stats</code> role are allowed to see the SQL text and279 <code class="structfield">queryid</code> of queries executed by other users.280 Other users can see the statistics, however, if the view has been installed281 in their database.282 </p><p>283 Plannable queries (that is, <code class="command">SELECT</code>, <code class="command">INSERT</code>,284 <code class="command">UPDATE</code>, <code class="command">DELETE</code>, and <code class="command">MERGE</code>)285 and utility commands are combined into a single286 <code class="structname">pg_stat_statements</code> entry whenever they have identical query287 structures according to an internal hash calculation. Typically, two288 queries will be considered the same for this purpose if they are289 semantically equivalent except for the values of literal constants290 appearing in the query.291 </p><div class="note"><h3 class="title">Note</h3><p>292 The following details about constant replacement and293 <code class="structfield">queryid</code> only apply when <a class="xref" href="runtime-config-statistics.html#GUC-COMPUTE-QUERY-ID">compute_query_id</a> is enabled. If you use an external294 module instead to compute <code class="structfield">queryid</code>, you295 should refer to its documentation for details.296 </p></div><p>297 When a constant's value has been ignored for purposes of matching the query298 to other queries, the constant is replaced by a parameter symbol, such299 as <code class="literal">$1</code>, in the <code class="structname">pg_stat_statements</code>300 display.301 The rest of the query text is that of the first query that had the302 particular <code class="structfield">queryid</code> hash value associated with the303 <code class="structname">pg_stat_statements</code> entry.304 </p><p>305 Queries on which normalization can be applied may be observed with constant306 values in <code class="structname">pg_stat_statements</code>, especially when there307 is a high rate of entry deallocations. To reduce the likelihood of this308 happening, consider increasing <code class="varname">pg_stat_statements.max</code>.309 The <code class="structname">pg_stat_statements_info</code> view, discussed below310 in <a class="xref" href="pgstatstatements.html#PGSTATSTATEMENTS-PG-STAT-STATEMENTS-INFO" title="F.32.2. The pg_stat_statements_info View">Section F.32.2</a>,311 provides statistics about entry deallocations.312 </p><p>313 In some cases, queries with visibly different texts might get merged into a314 single <code class="structname">pg_stat_statements</code> entry. Normally this will happen315 only for semantically equivalent queries, but there is a small chance of316 hash collisions causing unrelated queries to be merged into one entry.317 (This cannot happen for queries belonging to different users or databases,318 however.)319 </p><p>320 Since the <code class="structfield">queryid</code> hash value is computed on the321 post-parse-analysis representation of the queries, the opposite is322 also possible: queries with identical texts might appear as323 separate entries, if they have different meanings as a result of324 factors such as different <code class="varname">search_path</code> settings.325 </p><p>326 Consumers of <code class="structname">pg_stat_statements</code> may wish to use327 <code class="structfield">queryid</code> (perhaps in combination with328 <code class="structfield">dbid</code> and <code class="structfield">userid</code>) as a more stable329 and reliable identifier for each entry than its query text.330 However, it is important to understand that there are only limited331 guarantees around the stability of the <code class="structfield">queryid</code> hash332 value. Since the identifier is derived from the333 post-parse-analysis tree, its value is a function of, among other334 things, the internal object identifiers appearing in this representation.335 This has some counterintuitive implications. For example,336 <code class="filename">pg_stat_statements</code> will consider two apparently-identical337 queries to be distinct, if they reference a table that was dropped338 and recreated between the executions of the two queries.339 The hashing process is also sensitive to differences in340 machine architecture and other facets of the platform.341 Furthermore, it is not safe to assume that <code class="structfield">queryid</code>342 will be stable across major versions of <span class="productname">PostgreSQL</span>.343 </p><p>344 Two servers participating in replication based on physical WAL replay can345 be expected to have identical <code class="structfield">queryid</code> values for346 the same query. However, logical replication schemes do not promise to347 keep replicas identical in all relevant details, so348 <code class="structfield">queryid</code> will not be a useful identifier for349 accumulating costs across a set of logical replicas.350 If in doubt, direct testing is recommended.351 </p><p>352 Generally, it can be assumed that <code class="structfield">queryid</code> values353 are stable between minor version releases of <span class="productname">PostgreSQL</span>,354 providing that instances are running on the same machine architecture and355 the catalog metadata details match. Compatibility will only be broken356 between minor versions as a last resort.357 </p><p>358 The parameter symbols used to replace constants in359 representative query texts start from the next number after the360 highest <code class="literal">$</code><em class="replaceable"><code>n</code></em> parameter in the original query361 text, or <code class="literal">$1</code> if there was none. It's worth noting that in362 some cases there may be hidden parameter symbols that affect this363 numbering. For example, <span class="application">PL/pgSQL</span> uses hidden parameter364 symbols to insert values of function local variables into queries, so that365 a <span class="application">PL/pgSQL</span> statement like <code class="literal">SELECT i + 1 INTO j</code>366 would have representative text like <code class="literal">SELECT i + $2</code>.367 </p><p>368 The representative query texts are kept in an external disk file, and do369 not consume shared memory. Therefore, even very lengthy query texts can370 be stored successfully. However, if many long query texts are371 accumulated, the external file might grow unmanageably large. As a372 recovery method if that happens, <code class="filename">pg_stat_statements</code> may373 choose to discard the query texts, whereupon all existing entries in374 the <code class="structname">pg_stat_statements</code> view will show375 null <code class="structfield">query</code> fields, though the statistics associated with376 each <code class="structfield">queryid</code> are preserved. If this happens, consider377 reducing <code class="varname">pg_stat_statements.max</code> to prevent378 recurrences.379 </p><p>380 <code class="structfield">plans</code> and <code class="structfield">calls</code> aren't381 always expected to match because planning and execution statistics are382 updated at their respective end phase, and only for successful operations.383 For example, if a statement is successfully planned but fails during384 the execution phase, only its planning statistics will be updated.385 If planning is skipped because a cached plan is used, only its execution386 statistics will be updated.387 </p></div><div class="sect2" id="PGSTATSTATEMENTS-PG-STAT-STATEMENTS-INFO"><div class="titlepage"><div><div><h3 class="title">F.32.2. The <code class="structname">pg_stat_statements_info</code> View <a href="#PGSTATSTATEMENTS-PG-STAT-STATEMENTS-INFO" class="id_link">#</a></h3></div></div></div><a id="id-1.11.7.42.7.2" class="indexterm"></a><p>388 The statistics of the <code class="filename">pg_stat_statements</code> module389 itself are tracked and made available via a view named390 <code class="structname">pg_stat_statements_info</code>. This view contains391 only a single row. The columns of the view are shown in392 <a class="xref" href="pgstatstatements.html#PGSTATSTATEMENTSINFO-COLUMNS" title="Table F.23. pg_stat_statements_info Columns">Table F.23</a>.393 </p><div class="table" id="PGSTATSTATEMENTSINFO-COLUMNS"><p class="title"><strong>Table F.23. <code class="structname">pg_stat_statements_info</code> Columns</strong></p><div class="table-contents"><table class="table" summary="pg_stat_statements_info Columns" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">394 Column Type395 </p>396 <p>397 Description398 </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">399 <code class="structfield">dealloc</code> <code class="type">bigint</code>400 </p>401 <p>402 Total number of times <code class="structname">pg_stat_statements</code>403 entries about the least-executed statements were deallocated404 because more distinct statements than405 <code class="varname">pg_stat_statements.max</code> were observed406 </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">407 <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code>408 </p>409 <p>410 Time at which all statistics in the411 <code class="structname">pg_stat_statements</code> view were last reset.412 </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="PGSTATSTATEMENTS-FUNCS"><div class="titlepage"><div><div><h3 class="title">F.32.3. Functions <a href="#PGSTATSTATEMENTS-FUNCS" class="id_link">#</a></h3></div></div></div><div class="variablelist"><dl class="variablelist"><dt><span class="term">413 <code class="function">pg_stat_statements_reset(userid Oid, dbid Oid, queryid bigint) returns void</code>414 <a id="id-1.11.7.42.8.2.1.1.2" class="indexterm"></a>415 </span></dt><dd><p>416 <code class="function">pg_stat_statements_reset</code> discards statistics417 gathered so far by <code class="filename">pg_stat_statements</code> corresponding418 to the specified <code class="structfield">userid</code>, <code class="structfield">dbid</code>419 and <code class="structfield">queryid</code>. If any of the parameters are not420 specified, the default value <code class="literal">0</code>(invalid) is used for421 each of them and the statistics that match with other parameters will be422 reset. If no parameter is specified or all the specified parameters are423 <code class="literal">0</code>(invalid), it will discard all statistics.424 If all statistics in the <code class="filename">pg_stat_statements</code>425 view are discarded, it will also reset the statistics in the426 <code class="structname">pg_stat_statements_info</code> view.427 By default, this function can only be executed by superusers.428 Access may be granted to others using <code class="command">GRANT</code>.429 </p></dd><dt><span class="term">430 <code class="function">pg_stat_statements(showtext boolean) returns setof record</code>431 <a id="id-1.11.7.42.8.2.2.1.2" class="indexterm"></a>432 </span></dt><dd><p>433 The <code class="structname">pg_stat_statements</code> view is defined in434 terms of a function also named <code class="function">pg_stat_statements</code>.435 It is possible for clients to call436 the <code class="function">pg_stat_statements</code> function directly, and by437 specifying <code class="literal">showtext := false</code> have query text be438 omitted (that is, the <code class="literal">OUT</code> argument that corresponds439 to the view's <code class="structfield">query</code> column will return nulls). This440 feature is intended to support external tools that might wish to avoid441 the overhead of repeatedly retrieving query texts of indeterminate442 length. Such tools can instead cache the first query text observed443 for each entry themselves, since that is444 all <code class="filename">pg_stat_statements</code> itself does, and then retrieve445 query texts only as needed. Since the server stores query texts in a446 file, this approach may reduce physical I/O for repeated examination447 of the <code class="structname">pg_stat_statements</code> data.448 </p></dd></dl></div></div><div class="sect2" id="PGSTATSTATEMENTS-CONFIG-PARAMS"><div class="titlepage"><div><div><h3 class="title">F.32.4. Configuration Parameters <a href="#PGSTATSTATEMENTS-CONFIG-PARAMS" class="id_link">#</a></h3></div></div></div><div class="variablelist"><dl class="variablelist"><dt><span class="term">449 <code class="varname">pg_stat_statements.max</code> (<code class="type">integer</code>)450 <a id="id-1.11.7.42.9.2.1.1.3" class="indexterm"></a>451 </span></dt><dd><p>452 <code class="varname">pg_stat_statements.max</code> is the maximum number of453 statements tracked by the module (i.e., the maximum number of rows454 in the <code class="structname">pg_stat_statements</code> view). If more distinct455 statements than that are observed, information about the least-executed456 statements is discarded. The number of times such information was457 discarded can be seen in the458 <code class="structname">pg_stat_statements_info</code> view.459 The default value is 5000.460 This parameter can only be set at server start.461 </p></dd><dt><span class="term">462 <code class="varname">pg_stat_statements.track</code> (<code class="type">enum</code>)463 <a id="id-1.11.7.42.9.2.2.1.3" class="indexterm"></a>464 </span></dt><dd><p>465 <code class="varname">pg_stat_statements.track</code> controls which statements466 are counted by the module.467 Specify <code class="literal">top</code> to track top-level statements (those issued468 directly by clients), <code class="literal">all</code> to also track nested statements469 (such as statements invoked within functions), or <code class="literal">none</code> to470 disable statement statistics collection.471 The default value is <code class="literal">top</code>.472 Only superusers can change this setting.473 </p></dd><dt><span class="term">474 <code class="varname">pg_stat_statements.track_utility</code> (<code class="type">boolean</code>)475 <a id="id-1.11.7.42.9.2.3.1.3" class="indexterm"></a>476 </span></dt><dd><p>477 <code class="varname">pg_stat_statements.track_utility</code> controls whether478 utility commands are tracked by the module. Utility commands are479 all those other than <code class="command">SELECT</code>, <code class="command">INSERT</code>,480 <code class="command">UPDATE</code>, <code class="command">DELETE</code>, and <code class="command">MERGE</code>.481 The default value is <code class="literal">on</code>.482 Only superusers can change this setting.483 </p></dd><dt><span class="term">484 <code class="varname">pg_stat_statements.track_planning</code> (<code class="type">boolean</code>)485 <a id="id-1.11.7.42.9.2.4.1.3" class="indexterm"></a>486 </span></dt><dd><p>487 <code class="varname">pg_stat_statements.track_planning</code> controls whether488 planning operations and duration are tracked by the module.489 Enabling this parameter may incur a noticeable performance penalty,490 especially when statements with identical query structure are executed491 by many concurrent connections which compete to update a small number of492 <code class="structname">pg_stat_statements</code> entries.493 The default value is <code class="literal">off</code>.494 Only superusers can change this setting.495 </p></dd><dt><span class="term">496 <code class="varname">pg_stat_statements.save</code> (<code class="type">boolean</code>)497 <a id="id-1.11.7.42.9.2.5.1.3" class="indexterm"></a>498 </span></dt><dd><p>499 <code class="varname">pg_stat_statements.save</code> specifies whether to500 save statement statistics across server shutdowns.501 If it is <code class="literal">off</code> then statistics are not saved at502 shutdown nor reloaded at server start.503 The default value is <code class="literal">on</code>.504 This parameter can only be set in the <code class="filename">postgresql.conf</code>505 file or on the server command line.506 </p></dd></dl></div><p>507 The module requires additional shared memory proportional to508 <code class="varname">pg_stat_statements.max</code>. Note that this509 memory is consumed whenever the module is loaded, even if510 <code class="varname">pg_stat_statements.track</code> is set to <code class="literal">none</code>.511 </p><p>512 These parameters must be set in <code class="filename">postgresql.conf</code>.513 Typical usage might be:514 515</p><pre class="programlisting">516# postgresql.conf517shared_preload_libraries = 'pg_stat_statements'518 519compute_query_id = on520pg_stat_statements.max = 10000521pg_stat_statements.track = all522</pre><p>523 </p></div><div class="sect2" id="PGSTATSTATEMENTS-SAMPLE-OUTPUT"><div class="titlepage"><div><div><h3 class="title">F.32.5. Sample Output <a href="#PGSTATSTATEMENTS-SAMPLE-OUTPUT" class="id_link">#</a></h3></div></div></div><pre class="screen">524bench=# SELECT pg_stat_statements_reset();525 526$ pgbench -i bench527$ pgbench -c10 -t300 bench528 529bench=# \x530bench=# SELECT query, calls, total_exec_time, rows, 100.0 * shared_blks_hit /531 nullif(shared_blks_hit + shared_blks_read, 0) AS hit_percent532 FROM pg_stat_statements ORDER BY total_exec_time DESC LIMIT 5;533-[ RECORD 1 ]---+--------------------------------------------------------------------534query | UPDATE pgbench_branches SET bbalance = bbalance + $1 WHERE bid = $2535calls | 3000536total_exec_time | 25565.855387537rows | 3000538hit_percent | 100.0000000000000000539-[ RECORD 2 ]---+--------------------------------------------------------------------540query | UPDATE pgbench_tellers SET tbalance = tbalance + $1 WHERE tid = $2541calls | 3000542total_exec_time | 20756.669379543rows | 3000544hit_percent | 100.0000000000000000545-[ RECORD 3 ]---+--------------------------------------------------------------------546query | copy pgbench_accounts from stdin547calls | 1548total_exec_time | 291.865911549rows | 100000550hit_percent | 100.0000000000000000551-[ RECORD 4 ]---+--------------------------------------------------------------------552query | UPDATE pgbench_accounts SET abalance = abalance + $1 WHERE aid = $2553calls | 3000554total_exec_time | 271.232977555rows | 3000556hit_percent | 98.8454011741682975557-[ RECORD 5 ]---+--------------------------------------------------------------------558query | alter table pgbench_accounts add primary key (aid)559calls | 1560total_exec_time | 160.588563561rows | 0562hit_percent | 100.0000000000000000563 564 565bench=# SELECT pg_stat_statements_reset(0,0,s.queryid) FROM pg_stat_statements AS s566 WHERE s.query = 'UPDATE pgbench_branches SET bbalance = bbalance + $1 WHERE bid = $2';567 568bench=# SELECT query, calls, total_exec_time, rows, 100.0 * shared_blks_hit /569 nullif(shared_blks_hit + shared_blks_read, 0) AS hit_percent570 FROM pg_stat_statements ORDER BY total_exec_time DESC LIMIT 5;571-[ RECORD 1 ]---+--------------------------------------------------------------------572query | UPDATE pgbench_tellers SET tbalance = tbalance + $1 WHERE tid = $2573calls | 3000574total_exec_time | 20756.669379575rows | 3000576hit_percent | 100.0000000000000000577-[ RECORD 2 ]---+--------------------------------------------------------------------578query | copy pgbench_accounts from stdin579calls | 1580total_exec_time | 291.865911581rows | 100000582hit_percent | 100.0000000000000000583-[ RECORD 3 ]---+--------------------------------------------------------------------584query | UPDATE pgbench_accounts SET abalance = abalance + $1 WHERE aid = $2585calls | 3000586total_exec_time | 271.232977587rows | 3000588hit_percent | 98.8454011741682975589-[ RECORD 4 ]---+--------------------------------------------------------------------590query | alter table pgbench_accounts add primary key (aid)591calls | 1592total_exec_time | 160.588563593rows | 0594hit_percent | 100.0000000000000000595-[ RECORD 5 ]---+--------------------------------------------------------------------596query | vacuum analyze pgbench_accounts597calls | 1598total_exec_time | 136.448116599rows | 0600hit_percent | 99.9201915403032721601 602bench=# SELECT pg_stat_statements_reset(0,0,0);603 604bench=# SELECT query, calls, total_exec_time, rows, 100.0 * shared_blks_hit /605 nullif(shared_blks_hit + shared_blks_read, 0) AS hit_percent606 FROM pg_stat_statements ORDER BY total_exec_time DESC LIMIT 5;607-[ RECORD 1 ]---+-----------------------------------------------------------------------------608query | SELECT pg_stat_statements_reset(0,0,0)609calls | 1610total_exec_time | 0.189497611rows | 1612hit_percent |613-[ RECORD 2 ]---+-----------------------------------------------------------------------------614query | SELECT query, calls, total_exec_time, rows, $1 * shared_blks_hit / +615 | nullif(shared_blks_hit + shared_blks_read, $2) AS hit_percent+616 | FROM pg_stat_statements ORDER BY total_exec_time DESC LIMIT $3617calls | 0618total_exec_time | 0619rows | 0620hit_percent |621 622</pre></div><div class="sect2" id="PGSTATSTATEMENTS-AUTHORS"><div class="titlepage"><div><div><h3 class="title">F.32.6. Authors <a href="#PGSTATSTATEMENTS-AUTHORS" class="id_link">#</a></h3></div></div></div><p>623 Takahiro Itagaki <code class="email"><<a class="email" href="mailto:itagaki.takahiro@oss.ntt.co.jp">itagaki.takahiro@oss.ntt.co.jp</a>></code>.624 Query normalization added by Peter Geoghegan <code class="email"><<a class="email" href="mailto:peter@2ndquadrant.com">peter@2ndquadrant.com</a>></code>.625 </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="pgrowlocks.html" title="F.31. pgrowlocks — show a table's row locking information">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="contrib.html" title="Appendix F. Additional Supplied Modules and Extensions">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="pgstattuple.html" title="F.33. pgstattuple — obtain tuple-level statistics">Next</a></td></tr><tr><td width="40%" align="left" valign="top">F.31. pgrowlocks — show a table's row locking information </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="40%" align="right" valign="top"> F.33. pgstattuple — obtain tuple-level statistics</td></tr></table></div></body></html>