Line data    Source code

       1              : /*--------------------------------------------------------------------------
       2              :  *
       3              :  * regress_injection.c
       4              :  *      Functions supporting test-specific subject matter.
       5              :  *
       6              :  * Portions Copyright (c) 1996-2026, 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           43 : PG_FUNCTION_INFO_V1(removable_cutoff);
      41              : Datum
      42            9 : removable_cutoff(PG_FUNCTION_ARGS)
      43              : {
      44            9 :     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            9 :     if (!PG_ARGISNULL(0))
      51            9 :         rel = table_open(PG_GETARG_OID(0), AccessShareLock);
      52              : 
      53            9 :     if (rel != NULL && !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            9 :     next_fxid = ReadNextFullTransactionId();
      65              :     do
      66              :     {
      67            9 :         CHECK_FOR_INTERRUPTS();
      68            9 :         next_fxid_before = next_fxid;
      69            9 :         xid = GetOldestNonRemovableTransactionId(rel);
      70            9 :         next_fxid = ReadNextFullTransactionId();
      71            9 :     } while (!FullTransactionIdEquals(next_fxid, next_fxid_before));
      72              : 
      73            9 :     if (rel)
      74            9 :         table_close(rel, AccessShareLock);
      75              : 
      76            9 :     PG_RETURN_FULLTRANSACTIONID(FullTransactionIdFromAllowableAt(next_fxid,
      77              :                                                                  xid));
      78              : }