Line data    Source code

       1             : /*--------------------------------------------------------------------------
       2             :  *
       3             :  * regress_injection.c
       4             :  *      Functions supporting test-specific subject matter.
       5             :  *
       6             :  * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
       7             :  * Portions Copyright (c) 1994, Regents of the University of California
       8             :  *
       9             :  * IDENTIFICATION
      10             :  *      src/test/modules/injection_points/regress_injection.c
      11             :  *
      12             :  * -------------------------------------------------------------------------
      13             :  */
      14             : 
      15             : #include "postgres.h"
      16             : 
      17             : #include "access/table.h"
      18             : #include "fmgr.h"
      19             : #include "miscadmin.h"
      20             : #include "postmaster/autovacuum.h"
      21             : #include "storage/procarray.h"
      22             : #include "utils/rel.h"
      23             : #include "utils/xid8.h"
      24             : 
      25             : /*
      26             :  * removable_cutoff - for syscache-update-pruned.spec
      27             :  *
      28             :  * Wrapper around GetOldestNonRemovableTransactionId().  In general, this can
      29             :  * move backward.  runningcheck=false isolation tests can reasonably prevent
      30             :  * that.  For the causes of backward movement, see
      31             :  * postgr.es/m/CAEze2Wj%2BV0kTx86xB_YbyaqTr5hnE_igdWAwuhSyjXBYscf5-Q%40mail.gmail.com
      32             :  * and the header comment for ComputeXidHorizons().  One can assume this
      33             :  * doesn't move backward if one (a) passes a shared catalog as the argument
      34             :  * and (b) arranges for concurrent activity not to reach AbortTransaction().
      35             :  * Non-runningcheck tests can control most concurrent activity, except
      36             :  * autovacuum and the isolationtester control connection.  AbortTransaction()
      37             :  * in those would justify test failure.  Seeing autoanalyze can allocate an
      38             :  * XID in any database, (a) ensures we'll consistently not ignore those XIDs.
      39             :  */
      40          68 : PG_FUNCTION_INFO_V1(removable_cutoff);
      41             : Datum
      42          18 : removable_cutoff(PG_FUNCTION_ARGS)
      43             : {
      44          18 :     Relation    rel = NULL;
      45             :     TransactionId xid;
      46             :     FullTransactionId next_fxid_before,
      47             :                 next_fxid;
      48             : 
      49             :     /* could take other relkinds callee takes, but we've not yet needed it */
      50          18 :     if (!PG_ARGISNULL(0))
      51          18 :         rel = table_open(PG_GETARG_OID(0), AccessShareLock);
      52             : 
      53          18 :     if (!rel->rd_rel->relisshared && autovacuum_start_daemon)
      54           0 :         elog(WARNING,
      55             :              "removable_cutoff(non-shared-rel) can move backward under autovacuum=on");
      56             : 
      57             :     /*
      58             :      * No lock or snapshot necessarily prevents oldestXid from advancing past
      59             :      * "xid" while this function runs.  That concerns us only in that we must
      60             :      * not ascribe "xid" to the wrong epoch.  (That may never arise in
      61             :      * isolation testing, but let's set a good example.)  As a crude solution,
      62             :      * retry until nextXid doesn't change.
      63             :      */
      64          18 :     next_fxid = ReadNextFullTransactionId();
      65             :     do
      66             :     {
      67          18 :         CHECK_FOR_INTERRUPTS();
      68          18 :         next_fxid_before = next_fxid;
      69          18 :         xid = GetOldestNonRemovableTransactionId(rel);
      70          18 :         next_fxid = ReadNextFullTransactionId();
      71          18 :     } while (!FullTransactionIdEquals(next_fxid, next_fxid_before));
      72             : 
      73          18 :     if (rel)
      74          18 :         table_close(rel, AccessShareLock);
      75             : 
      76          18 :     PG_RETURN_FULLTRANSACTIONID(FullTransactionIdFromAllowableAt(next_fxid,
      77             :                                                                  xid));
      78             : }