Line data    Source code

       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * delay_execution.c
       4             :  *      Test module to allow delay between parsing and execution of a query.
       5             :  *
       6             :  * The delay is implemented by taking and immediately releasing a specified
       7             :  * advisory lock.  If another process has previously taken that lock, the
       8             :  * current process will be blocked until the lock is released; otherwise,
       9             :  * there's no effect.  This allows an isolationtester script to reliably
      10             :  * test behaviors where some specified action happens in another backend
      11             :  * between parsing and execution of any desired query.
      12             :  *
      13             :  * Copyright (c) 2020-2025, PostgreSQL Global Development Group
      14             :  *
      15             :  * IDENTIFICATION
      16             :  *    src/test/modules/delay_execution/delay_execution.c
      17             :  *
      18             :  *-------------------------------------------------------------------------
      19             :  */
      20             : 
      21             : #include "postgres.h"
      22             : 
      23             : #include <limits.h>
      24             : 
      25             : #include "optimizer/planner.h"
      26             : #include "utils/fmgrprotos.h"
      27             : #include "utils/guc.h"
      28             : #include "utils/inval.h"
      29             : 
      30             : 
      31           4 : PG_MODULE_MAGIC;
      32             : 
      33             : /* GUC: advisory lock ID to use.  Zero disables the feature. */
      34             : static int  post_planning_lock_id = 0;
      35             : 
      36             : /* Save previous planner hook user to be a good citizen */
      37             : static planner_hook_type prev_planner_hook = NULL;
      38             : 
      39             : 
      40             : /* planner_hook function to provide the desired delay */
      41             : static PlannedStmt *
      42          30 : delay_execution_planner(Query *parse, const char *query_string,
      43             :                         int cursorOptions, ParamListInfo boundParams,
      44             :                         ExplainState *es)
      45             : {
      46             :     PlannedStmt *result;
      47             : 
      48             :     /* Invoke the planner, possibly via a previous hook user */
      49          30 :     if (prev_planner_hook)
      50           0 :         result = prev_planner_hook(parse, query_string, cursorOptions,
      51             :                                    boundParams, es);
      52             :     else
      53          30 :         result = standard_planner(parse, query_string, cursorOptions,
      54             :                                   boundParams, es);
      55             : 
      56             :     /* If enabled, delay by taking and releasing the specified lock */
      57          30 :     if (post_planning_lock_id != 0)
      58             :     {
      59          30 :         DirectFunctionCall1(pg_advisory_lock_int8,
      60             :                             Int64GetDatum((int64) post_planning_lock_id));
      61          30 :         DirectFunctionCall1(pg_advisory_unlock_int8,
      62             :                             Int64GetDatum((int64) post_planning_lock_id));
      63             : 
      64             :         /*
      65             :          * Ensure that we notice any pending invalidations, since the advisory
      66             :          * lock functions don't do this.
      67             :          */
      68          30 :         AcceptInvalidationMessages();
      69             :     }
      70             : 
      71          30 :     return result;
      72             : }
      73             : 
      74             : /* Module load function */
      75             : void
      76           4 : _PG_init(void)
      77             : {
      78             :     /* Set up the GUC to control which lock is used */
      79           4 :     DefineCustomIntVariable("delay_execution.post_planning_lock_id",
      80             :                             "Sets the advisory lock ID to be locked/unlocked after planning.",
      81             :                             "Zero disables the delay.",
      82             :                             &post_planning_lock_id,
      83             :                             0,
      84             :                             0, INT_MAX,
      85             :                             PGC_USERSET,
      86             :                             0,
      87             :                             NULL,
      88             :                             NULL,
      89             :                             NULL);
      90             : 
      91           4 :     MarkGUCPrefixReserved("delay_execution");
      92             : 
      93             :     /* Install our hook */
      94           4 :     prev_planner_hook = planner_hook;
      95           4 :     planner_hook = delay_execution_planner;
      96           4 : }