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 "storage/procarray.h"
      21             : #include "utils/xid8.h"
      22             : 
      23             : /*
      24             :  * removable_cutoff - for syscache-update-pruned.spec
      25             :  *
      26             :  * Wrapper around GetOldestNonRemovableTransactionId().  In general, this can
      27             :  * move backward.  runningcheck=false isolation tests can reasonably prevent
      28             :  * that.  For the causes of backward movement, see
      29             :  * postgr.es/m/CAEze2Wj%2BV0kTx86xB_YbyaqTr5hnE_igdWAwuhSyjXBYscf5-Q%40mail.gmail.com
      30             :  * and the header comment for ComputeXidHorizons().  One can assume this
      31             :  * doesn't move backward if one arranges for concurrent activity not to reach
      32             :  * AbortTransaction() and not to allocate an XID while connected to another
      33             :  * database.  Non-runningcheck tests can control most concurrent activity,
      34             :  * except autovacuum and the isolationtester control connection.  Neither
      35             :  * allocates XIDs, and AbortTransaction() in those would justify test failure.
      36             :  */
      37          66 : PG_FUNCTION_INFO_V1(removable_cutoff);
      38             : Datum
      39          12 : removable_cutoff(PG_FUNCTION_ARGS)
      40             : {
      41          12 :     Relation    rel = NULL;
      42             :     TransactionId xid;
      43             :     FullTransactionId next_fxid_before,
      44             :                 next_fxid;
      45             : 
      46             :     /* could take other relkinds callee takes, but we've not yet needed it */
      47          12 :     if (!PG_ARGISNULL(0))
      48          12 :         rel = table_open(PG_GETARG_OID(0), AccessShareLock);
      49             : 
      50             :     /*
      51             :      * No lock or snapshot necessarily prevents oldestXid from advancing past
      52             :      * "xid" while this function runs.  That concerns us only in that we must
      53             :      * not ascribe "xid" to the wrong epoch.  (That may never arise in
      54             :      * isolation testing, but let's set a good example.)  As a crude solution,
      55             :      * retry until nextXid doesn't change.
      56             :      */
      57          12 :     next_fxid = ReadNextFullTransactionId();
      58             :     do
      59             :     {
      60          12 :         CHECK_FOR_INTERRUPTS();
      61          12 :         next_fxid_before = next_fxid;
      62          12 :         xid = GetOldestNonRemovableTransactionId(rel);
      63          12 :         next_fxid = ReadNextFullTransactionId();
      64          12 :     } while (!FullTransactionIdEquals(next_fxid, next_fxid_before));
      65             : 
      66          12 :     if (rel)
      67          12 :         table_close(rel, AccessShareLock);
      68             : 
      69          12 :     PG_RETURN_FULLTRANSACTIONID(FullTransactionIdFromAllowableAt(next_fxid,
      70             :                                                                  xid));
      71             : }