LCOV - code coverage report
Current view: top level - src/backend/access/index - genam.c (source / functions) Hit Total Coverage
Test: PostgreSQL 18devel Lines: 161 192 83.9 %
Date: 2024-07-19 16:11:31 Functions: 11 12 91.7 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * genam.c
       4             :  *    general index access method routines
       5             :  *
       6             :  * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
       7             :  * Portions Copyright (c) 1994, Regents of the University of California
       8             :  *
       9             :  *
      10             :  * IDENTIFICATION
      11             :  *    src/backend/access/index/genam.c
      12             :  *
      13             :  * NOTES
      14             :  *    many of the old access method routines have been turned into
      15             :  *    macros and moved to genam.h -cim 4/30/91
      16             :  *
      17             :  *-------------------------------------------------------------------------
      18             :  */
      19             : 
      20             : #include "postgres.h"
      21             : 
      22             : #include "access/genam.h"
      23             : #include "access/relscan.h"
      24             : #include "access/tableam.h"
      25             : #include "access/transam.h"
      26             : #include "catalog/index.h"
      27             : #include "lib/stringinfo.h"
      28             : #include "miscadmin.h"
      29             : #include "storage/bufmgr.h"
      30             : #include "storage/procarray.h"
      31             : #include "utils/acl.h"
      32             : #include "utils/lsyscache.h"
      33             : #include "utils/rel.h"
      34             : #include "utils/rls.h"
      35             : #include "utils/ruleutils.h"
      36             : #include "utils/snapmgr.h"
      37             : 
      38             : 
      39             : /* ----------------------------------------------------------------
      40             :  *      general access method routines
      41             :  *
      42             :  *      All indexed access methods use an identical scan structure.
      43             :  *      We don't know how the various AMs do locking, however, so we don't
      44             :  *      do anything about that here.
      45             :  *
      46             :  *      The intent is that an AM implementor will define a beginscan routine
      47             :  *      that calls RelationGetIndexScan, to fill in the scan, and then does
      48             :  *      whatever kind of locking he wants.
      49             :  *
      50             :  *      At the end of a scan, the AM's endscan routine undoes the locking,
      51             :  *      but does *not* call IndexScanEnd --- the higher-level index_endscan
      52             :  *      routine does that.  (We can't do it in the AM because index_endscan
      53             :  *      still needs to touch the IndexScanDesc after calling the AM.)
      54             :  *
      55             :  *      Because of this, the AM does not have a choice whether to call
      56             :  *      RelationGetIndexScan or not; its beginscan routine must return an
      57             :  *      object made by RelationGetIndexScan.  This is kinda ugly but not
      58             :  *      worth cleaning up now.
      59             :  * ----------------------------------------------------------------
      60             :  */
      61             : 
      62             : /* ----------------
      63             :  *  RelationGetIndexScan -- Create and fill an IndexScanDesc.
      64             :  *
      65             :  *      This routine creates an index scan structure and sets up initial
      66             :  *      contents for it.
      67             :  *
      68             :  *      Parameters:
      69             :  *              indexRelation -- index relation for scan.
      70             :  *              nkeys -- count of scan keys (index qual conditions).
      71             :  *              norderbys -- count of index order-by operators.
      72             :  *
      73             :  *      Returns:
      74             :  *              An initialized IndexScanDesc.
      75             :  * ----------------
      76             :  */
      77             : IndexScanDesc
      78    10728714 : RelationGetIndexScan(Relation indexRelation, int nkeys, int norderbys)
      79             : {
      80             :     IndexScanDesc scan;
      81             : 
      82    10728714 :     scan = (IndexScanDesc) palloc(sizeof(IndexScanDescData));
      83             : 
      84    10728714 :     scan->heapRelation = NULL;   /* may be set later */
      85    10728714 :     scan->xs_heapfetch = NULL;
      86    10728714 :     scan->indexRelation = indexRelation;
      87    10728714 :     scan->xs_snapshot = InvalidSnapshot; /* caller must initialize this */
      88    10728714 :     scan->numberOfKeys = nkeys;
      89    10728714 :     scan->numberOfOrderBys = norderbys;
      90             : 
      91             :     /*
      92             :      * We allocate key workspace here, but it won't get filled until amrescan.
      93             :      */
      94    10728714 :     if (nkeys > 0)
      95    10716788 :         scan->keyData = (ScanKey) palloc(sizeof(ScanKeyData) * nkeys);
      96             :     else
      97       11926 :         scan->keyData = NULL;
      98    10728714 :     if (norderbys > 0)
      99         192 :         scan->orderByData = (ScanKey) palloc(sizeof(ScanKeyData) * norderbys);
     100             :     else
     101    10728522 :         scan->orderByData = NULL;
     102             : 
     103    10728714 :     scan->xs_want_itup = false; /* may be set later */
     104             : 
     105             :     /*
     106             :      * During recovery we ignore killed tuples and don't bother to kill them
     107             :      * either. We do this because the xmin on the primary node could easily be
     108             :      * later than the xmin on the standby node, so that what the primary
     109             :      * thinks is killed is supposed to be visible on standby. So for correct
     110             :      * MVCC for queries during recovery we must ignore these hints and check
     111             :      * all tuples. Do *not* set ignore_killed_tuples to true when running in a
     112             :      * transaction that was started during recovery. xactStartedInRecovery
     113             :      * should not be altered by index AMs.
     114             :      */
     115    10728714 :     scan->kill_prior_tuple = false;
     116    10728714 :     scan->xactStartedInRecovery = TransactionStartedDuringRecovery();
     117    10728714 :     scan->ignore_killed_tuples = !scan->xactStartedInRecovery;
     118             : 
     119    10728714 :     scan->opaque = NULL;
     120             : 
     121    10728714 :     scan->xs_itup = NULL;
     122    10728714 :     scan->xs_itupdesc = NULL;
     123    10728714 :     scan->xs_hitup = NULL;
     124    10728714 :     scan->xs_hitupdesc = NULL;
     125             : 
     126    10728714 :     return scan;
     127             : }
     128             : 
     129             : /* ----------------
     130             :  *  IndexScanEnd -- End an index scan.
     131             :  *
     132             :  *      This routine just releases the storage acquired by
     133             :  *      RelationGetIndexScan().  Any AM-level resources are
     134             :  *      assumed to already have been released by the AM's
     135             :  *      endscan routine.
     136             :  *
     137             :  *  Returns:
     138             :  *      None.
     139             :  * ----------------
     140             :  */
     141             : void
     142    10727296 : IndexScanEnd(IndexScanDesc scan)
     143             : {
     144    10727296 :     if (scan->keyData != NULL)
     145    10715418 :         pfree(scan->keyData);
     146    10727296 :     if (scan->orderByData != NULL)
     147         186 :         pfree(scan->orderByData);
     148             : 
     149    10727296 :     pfree(scan);
     150    10727296 : }
     151             : 
     152             : /*
     153             :  * BuildIndexValueDescription
     154             :  *
     155             :  * Construct a string describing the contents of an index entry, in the
     156             :  * form "(key_name, ...)=(key_value, ...)".  This is currently used
     157             :  * for building unique-constraint and exclusion-constraint error messages,
     158             :  * so only key columns of the index are checked and printed.
     159             :  *
     160             :  * Note that if the user does not have permissions to view all of the
     161             :  * columns involved then a NULL is returned.  Returning a partial key seems
     162             :  * unlikely to be useful and we have no way to know which of the columns the
     163             :  * user provided (unlike in ExecBuildSlotValueDescription).
     164             :  *
     165             :  * The passed-in values/nulls arrays are the "raw" input to the index AM,
     166             :  * e.g. results of FormIndexDatum --- this is not necessarily what is stored
     167             :  * in the index, but it's what the user perceives to be stored.
     168             :  *
     169             :  * Note: if you change anything here, check whether
     170             :  * ExecBuildSlotPartitionKeyDescription() in execMain.c needs a similar
     171             :  * change.
     172             :  */
     173             : char *
     174         750 : BuildIndexValueDescription(Relation indexRelation,
     175             :                            const Datum *values, const bool *isnull)
     176             : {
     177             :     StringInfoData buf;
     178             :     Form_pg_index idxrec;
     179             :     int         indnkeyatts;
     180             :     int         i;
     181             :     int         keyno;
     182         750 :     Oid         indexrelid = RelationGetRelid(indexRelation);
     183             :     Oid         indrelid;
     184             :     AclResult   aclresult;
     185             : 
     186         750 :     indnkeyatts = IndexRelationGetNumberOfKeyAttributes(indexRelation);
     187             : 
     188             :     /*
     189             :      * Check permissions- if the user does not have access to view all of the
     190             :      * key columns then return NULL to avoid leaking data.
     191             :      *
     192             :      * First check if RLS is enabled for the relation.  If so, return NULL to
     193             :      * avoid leaking data.
     194             :      *
     195             :      * Next we need to check table-level SELECT access and then, if there is
     196             :      * no access there, check column-level permissions.
     197             :      */
     198         750 :     idxrec = indexRelation->rd_index;
     199         750 :     indrelid = idxrec->indrelid;
     200             :     Assert(indexrelid == idxrec->indexrelid);
     201             : 
     202             :     /* RLS check- if RLS is enabled then we don't return anything. */
     203         750 :     if (check_enable_rls(indrelid, InvalidOid, true) == RLS_ENABLED)
     204          12 :         return NULL;
     205             : 
     206             :     /* Table-level SELECT is enough, if the user has it */
     207         738 :     aclresult = pg_class_aclcheck(indrelid, GetUserId(), ACL_SELECT);
     208         738 :     if (aclresult != ACLCHECK_OK)
     209             :     {
     210             :         /*
     211             :          * No table-level access, so step through the columns in the index and
     212             :          * make sure the user has SELECT rights on all of them.
     213             :          */
     214          24 :         for (keyno = 0; keyno < indnkeyatts; keyno++)
     215             :         {
     216          24 :             AttrNumber  attnum = idxrec->indkey.values[keyno];
     217             : 
     218             :             /*
     219             :              * Note that if attnum == InvalidAttrNumber, then this is an index
     220             :              * based on an expression and we return no detail rather than try
     221             :              * to figure out what column(s) the expression includes and if the
     222             :              * user has SELECT rights on them.
     223             :              */
     224          48 :             if (attnum == InvalidAttrNumber ||
     225          24 :                 pg_attribute_aclcheck(indrelid, attnum, GetUserId(),
     226             :                                       ACL_SELECT) != ACLCHECK_OK)
     227             :             {
     228             :                 /* No access, so clean up and return */
     229          12 :                 return NULL;
     230             :             }
     231             :         }
     232             :     }
     233             : 
     234         726 :     initStringInfo(&buf);
     235         726 :     appendStringInfo(&buf, "(%s)=(",
     236             :                      pg_get_indexdef_columns(indexrelid, true));
     237             : 
     238        1590 :     for (i = 0; i < indnkeyatts; i++)
     239             :     {
     240             :         char       *val;
     241             : 
     242         864 :         if (isnull[i])
     243          18 :             val = "null";
     244             :         else
     245             :         {
     246             :             Oid         foutoid;
     247             :             bool        typisvarlena;
     248             : 
     249             :             /*
     250             :              * The provided data is not necessarily of the type stored in the
     251             :              * index; rather it is of the index opclass's input type. So look
     252             :              * at rd_opcintype not the index tupdesc.
     253             :              *
     254             :              * Note: this is a bit shaky for opclasses that have pseudotype
     255             :              * input types such as ANYARRAY or RECORD.  Currently, the
     256             :              * typoutput functions associated with the pseudotypes will work
     257             :              * okay, but we might have to try harder in future.
     258             :              */
     259         846 :             getTypeOutputInfo(indexRelation->rd_opcintype[i],
     260             :                               &foutoid, &typisvarlena);
     261         846 :             val = OidOutputFunctionCall(foutoid, values[i]);
     262             :         }
     263             : 
     264         864 :         if (i > 0)
     265         138 :             appendStringInfoString(&buf, ", ");
     266         864 :         appendStringInfoString(&buf, val);
     267             :     }
     268             : 
     269         726 :     appendStringInfoChar(&buf, ')');
     270             : 
     271         726 :     return buf.data;
     272             : }
     273             : 
     274             : /*
     275             :  * Get the snapshotConflictHorizon from the table entries pointed to by the
     276             :  * index tuples being deleted using an AM-generic approach.
     277             :  *
     278             :  * This is a table_index_delete_tuples() shim used by index AMs that only need
     279             :  * to consult the tableam to get a snapshotConflictHorizon value, and only
     280             :  * expect to delete index tuples that are already known deletable (typically
     281             :  * due to having LP_DEAD bits set).  When a snapshotConflictHorizon value
     282             :  * isn't needed in index AM's deletion WAL record, it is safe for it to skip
     283             :  * calling here entirely.
     284             :  *
     285             :  * We assume that caller index AM uses the standard IndexTuple representation,
     286             :  * with table TIDs stored in the t_tid field.  We also expect (and assert)
     287             :  * that the line pointers on page for 'itemnos' offsets are already marked
     288             :  * LP_DEAD.
     289             :  */
     290             : TransactionId
     291           0 : index_compute_xid_horizon_for_tuples(Relation irel,
     292             :                                      Relation hrel,
     293             :                                      Buffer ibuf,
     294             :                                      OffsetNumber *itemnos,
     295             :                                      int nitems)
     296             : {
     297             :     TM_IndexDeleteOp delstate;
     298           0 :     TransactionId snapshotConflictHorizon = InvalidTransactionId;
     299           0 :     Page        ipage = BufferGetPage(ibuf);
     300             :     IndexTuple  itup;
     301             : 
     302             :     Assert(nitems > 0);
     303             : 
     304           0 :     delstate.irel = irel;
     305           0 :     delstate.iblknum = BufferGetBlockNumber(ibuf);
     306           0 :     delstate.bottomup = false;
     307           0 :     delstate.bottomupfreespace = 0;
     308           0 :     delstate.ndeltids = 0;
     309           0 :     delstate.deltids = palloc(nitems * sizeof(TM_IndexDelete));
     310           0 :     delstate.status = palloc(nitems * sizeof(TM_IndexStatus));
     311             : 
     312             :     /* identify what the index tuples about to be deleted point to */
     313           0 :     for (int i = 0; i < nitems; i++)
     314             :     {
     315           0 :         OffsetNumber offnum = itemnos[i];
     316             :         ItemId      iitemid;
     317             : 
     318           0 :         iitemid = PageGetItemId(ipage, offnum);
     319           0 :         itup = (IndexTuple) PageGetItem(ipage, iitemid);
     320             : 
     321             :         Assert(ItemIdIsDead(iitemid));
     322             : 
     323           0 :         ItemPointerCopy(&itup->t_tid, &delstate.deltids[i].tid);
     324           0 :         delstate.deltids[i].id = delstate.ndeltids;
     325           0 :         delstate.status[i].idxoffnum = offnum;
     326           0 :         delstate.status[i].knowndeletable = true;   /* LP_DEAD-marked */
     327           0 :         delstate.status[i].promising = false;   /* unused */
     328           0 :         delstate.status[i].freespace = 0;   /* unused */
     329             : 
     330           0 :         delstate.ndeltids++;
     331             :     }
     332             : 
     333             :     /* determine the actual xid horizon */
     334           0 :     snapshotConflictHorizon = table_index_delete_tuples(hrel, &delstate);
     335             : 
     336             :     /* assert tableam agrees that all items are deletable */
     337             :     Assert(delstate.ndeltids == nitems);
     338             : 
     339           0 :     pfree(delstate.deltids);
     340           0 :     pfree(delstate.status);
     341             : 
     342           0 :     return snapshotConflictHorizon;
     343             : }
     344             : 
     345             : 
     346             : /* ----------------------------------------------------------------
     347             :  *      heap-or-index-scan access to system catalogs
     348             :  *
     349             :  *      These functions support system catalog accesses that normally use
     350             :  *      an index but need to be capable of being switched to heap scans
     351             :  *      if the system indexes are unavailable.
     352             :  *
     353             :  *      The specified scan keys must be compatible with the named index.
     354             :  *      Generally this means that they must constrain either all columns
     355             :  *      of the index, or the first K columns of an N-column index.
     356             :  *
     357             :  *      These routines could work with non-system tables, actually,
     358             :  *      but they're only useful when there is a known index to use with
     359             :  *      the given scan keys; so in practice they're only good for
     360             :  *      predetermined types of scans of system catalogs.
     361             :  * ----------------------------------------------------------------
     362             :  */
     363             : 
     364             : /*
     365             :  * systable_beginscan --- set up for heap-or-index scan
     366             :  *
     367             :  *  rel: catalog to scan, already opened and suitably locked
     368             :  *  indexId: OID of index to conditionally use
     369             :  *  indexOK: if false, forces a heap scan (see notes below)
     370             :  *  snapshot: time qual to use (NULL for a recent catalog snapshot)
     371             :  *  nkeys, key: scan keys
     372             :  *
     373             :  * The attribute numbers in the scan key should be set for the heap case.
     374             :  * If we choose to index, we reset them to 1..n to reference the index
     375             :  * columns.  Note this means there must be one scankey qualification per
     376             :  * index column!  This is checked by the Asserts in the normal, index-using
     377             :  * case, but won't be checked if the heapscan path is taken.
     378             :  *
     379             :  * The routine checks the normal cases for whether an indexscan is safe,
     380             :  * but caller can make additional checks and pass indexOK=false if needed.
     381             :  * In standard case indexOK can simply be constant TRUE.
     382             :  */
     383             : SysScanDesc
     384    10543744 : systable_beginscan(Relation heapRelation,
     385             :                    Oid indexId,
     386             :                    bool indexOK,
     387             :                    Snapshot snapshot,
     388             :                    int nkeys, ScanKey key)
     389             : {
     390             :     SysScanDesc sysscan;
     391             :     Relation    irel;
     392             : 
     393    10543744 :     if (indexOK &&
     394    10359974 :         !IgnoreSystemIndexes &&
     395    10286614 :         !ReindexIsProcessingIndex(indexId))
     396    10275716 :         irel = index_open(indexId, AccessShareLock);
     397             :     else
     398      268028 :         irel = NULL;
     399             : 
     400    10543736 :     sysscan = (SysScanDesc) palloc(sizeof(SysScanDescData));
     401             : 
     402    10543736 :     sysscan->heap_rel = heapRelation;
     403    10543736 :     sysscan->irel = irel;
     404    10543736 :     sysscan->slot = table_slot_create(heapRelation, NULL);
     405             : 
     406    10543736 :     if (snapshot == NULL)
     407             :     {
     408     9573556 :         Oid         relid = RelationGetRelid(heapRelation);
     409             : 
     410     9573556 :         snapshot = RegisterSnapshot(GetCatalogSnapshot(relid));
     411     9573556 :         sysscan->snapshot = snapshot;
     412             :     }
     413             :     else
     414             :     {
     415             :         /* Caller is responsible for any snapshot. */
     416      970180 :         sysscan->snapshot = NULL;
     417             :     }
     418             : 
     419    10543736 :     if (irel)
     420             :     {
     421             :         int         i;
     422             : 
     423             :         /* Change attribute numbers to be index column numbers. */
     424    27272978 :         for (i = 0; i < nkeys; i++)
     425             :         {
     426             :             int         j;
     427             : 
     428    25058782 :             for (j = 0; j < IndexRelationGetNumberOfAttributes(irel); j++)
     429             :             {
     430    25058782 :                 if (key[i].sk_attno == irel->rd_index->indkey.values[j])
     431             :                 {
     432    16997270 :                     key[i].sk_attno = j + 1;
     433    16997270 :                     break;
     434             :                 }
     435             :             }
     436    16997270 :             if (j == IndexRelationGetNumberOfAttributes(irel))
     437           0 :                 elog(ERROR, "column is not in index");
     438             :         }
     439             : 
     440    10275708 :         sysscan->iscan = index_beginscan(heapRelation, irel,
     441             :                                          snapshot, nkeys, 0);
     442    10275708 :         index_rescan(sysscan->iscan, key, nkeys, NULL, 0);
     443    10275708 :         sysscan->scan = NULL;
     444             :     }
     445             :     else
     446             :     {
     447             :         /*
     448             :          * We disallow synchronized scans when forced to use a heapscan on a
     449             :          * catalog.  In most cases the desired rows are near the front, so
     450             :          * that the unpredictable start point of a syncscan is a serious
     451             :          * disadvantage; and there are no compensating advantages, because
     452             :          * it's unlikely that such scans will occur in parallel.
     453             :          */
     454      268028 :         sysscan->scan = table_beginscan_strat(heapRelation, snapshot,
     455             :                                               nkeys, key,
     456             :                                               true, false);
     457      268028 :         sysscan->iscan = NULL;
     458             :     }
     459             : 
     460             :     /*
     461             :      * If CheckXidAlive is set then set a flag to indicate that system table
     462             :      * scan is in-progress.  See detailed comments in xact.c where these
     463             :      * variables are declared.
     464             :      */
     465    10543736 :     if (TransactionIdIsValid(CheckXidAlive))
     466        1508 :         bsysscan = true;
     467             : 
     468    10543736 :     return sysscan;
     469             : }
     470             : 
     471             : /*
     472             :  * HandleConcurrentAbort - Handle concurrent abort of the CheckXidAlive.
     473             :  *
     474             :  * Error out, if CheckXidAlive is aborted. We can't directly use
     475             :  * TransactionIdDidAbort as after crash such transaction might not have been
     476             :  * marked as aborted.  See detailed comments in xact.c where the variable
     477             :  * is declared.
     478             :  */
     479             : static inline void
     480    21719584 : HandleConcurrentAbort()
     481             : {
     482    21719584 :     if (TransactionIdIsValid(CheckXidAlive) &&
     483        2212 :         !TransactionIdIsInProgress(CheckXidAlive) &&
     484          14 :         !TransactionIdDidCommit(CheckXidAlive))
     485          14 :         ereport(ERROR,
     486             :                 (errcode(ERRCODE_TRANSACTION_ROLLBACK),
     487             :                  errmsg("transaction aborted during system catalog scan")));
     488    21719570 : }
     489             : 
     490             : /*
     491             :  * systable_getnext --- get next tuple in a heap-or-index scan
     492             :  *
     493             :  * Returns NULL if no more tuples available.
     494             :  *
     495             :  * Note that returned tuple is a reference to data in a disk buffer;
     496             :  * it must not be modified, and should be presumed inaccessible after
     497             :  * next getnext() or endscan() call.
     498             :  *
     499             :  * XXX: It'd probably make sense to offer a slot based interface, at least
     500             :  * optionally.
     501             :  */
     502             : HeapTuple
     503    21317658 : systable_getnext(SysScanDesc sysscan)
     504             : {
     505    21317658 :     HeapTuple   htup = NULL;
     506             : 
     507    21317658 :     if (sysscan->irel)
     508             :     {
     509    19643206 :         if (index_getnext_slot(sysscan->iscan, ForwardScanDirection, sysscan->slot))
     510             :         {
     511             :             bool        shouldFree;
     512             : 
     513    14788642 :             htup = ExecFetchSlotHeapTuple(sysscan->slot, false, &shouldFree);
     514             :             Assert(!shouldFree);
     515             : 
     516             :             /*
     517             :              * We currently don't need to support lossy index operators for
     518             :              * any system catalog scan.  It could be done here, using the scan
     519             :              * keys to drive the operator calls, if we arranged to save the
     520             :              * heap attnums during systable_beginscan(); this is practical
     521             :              * because we still wouldn't need to support indexes on
     522             :              * expressions.
     523             :              */
     524    14788642 :             if (sysscan->iscan->xs_recheck)
     525           0 :                 elog(ERROR, "system catalog scans with lossy index conditions are not implemented");
     526             :         }
     527             :     }
     528             :     else
     529             :     {
     530     1674452 :         if (table_scan_getnextslot(sysscan->scan, ForwardScanDirection, sysscan->slot))
     531             :         {
     532             :             bool        shouldFree;
     533             : 
     534     1603572 :             htup = ExecFetchSlotHeapTuple(sysscan->slot, false, &shouldFree);
     535             :             Assert(!shouldFree);
     536             :         }
     537             :     }
     538             : 
     539             :     /*
     540             :      * Handle the concurrent abort while fetching the catalog tuple during
     541             :      * logical streaming of a transaction.
     542             :      */
     543    21317654 :     HandleConcurrentAbort();
     544             : 
     545    21317640 :     return htup;
     546             : }
     547             : 
     548             : /*
     549             :  * systable_recheck_tuple --- recheck visibility of most-recently-fetched tuple
     550             :  *
     551             :  * In particular, determine if this tuple would be visible to a catalog scan
     552             :  * that started now.  We don't handle the case of a non-MVCC scan snapshot,
     553             :  * because no caller needs that yet.
     554             :  *
     555             :  * This is useful to test whether an object was deleted while we waited to
     556             :  * acquire lock on it.
     557             :  *
     558             :  * Note: we don't actually *need* the tuple to be passed in, but it's a
     559             :  * good crosscheck that the caller is interested in the right tuple.
     560             :  */
     561             : bool
     562      192470 : systable_recheck_tuple(SysScanDesc sysscan, HeapTuple tup)
     563             : {
     564             :     Snapshot    freshsnap;
     565             :     bool        result;
     566             : 
     567             :     Assert(tup == ExecFetchSlotHeapTuple(sysscan->slot, false, NULL));
     568             : 
     569             :     /*
     570             :      * Trust that table_tuple_satisfies_snapshot() and its subsidiaries
     571             :      * (commonly LockBuffer() and HeapTupleSatisfiesMVCC()) do not themselves
     572             :      * acquire snapshots, so we need not register the snapshot.  Those
     573             :      * facilities are too low-level to have any business scanning tables.
     574             :      */
     575      192470 :     freshsnap = GetCatalogSnapshot(RelationGetRelid(sysscan->heap_rel));
     576             : 
     577      192470 :     result = table_tuple_satisfies_snapshot(sysscan->heap_rel,
     578      192470 :                                             sysscan->slot,
     579             :                                             freshsnap);
     580             : 
     581             :     /*
     582             :      * Handle the concurrent abort while fetching the catalog tuple during
     583             :      * logical streaming of a transaction.
     584             :      */
     585      192470 :     HandleConcurrentAbort();
     586             : 
     587      192470 :     return result;
     588             : }
     589             : 
     590             : /*
     591             :  * systable_endscan --- close scan, release resources
     592             :  *
     593             :  * Note that it's still up to the caller to close the heap relation.
     594             :  */
     595             : void
     596    10543202 : systable_endscan(SysScanDesc sysscan)
     597             : {
     598    10543202 :     if (sysscan->slot)
     599             :     {
     600    10543202 :         ExecDropSingleTupleTableSlot(sysscan->slot);
     601    10543202 :         sysscan->slot = NULL;
     602             :     }
     603             : 
     604    10543202 :     if (sysscan->irel)
     605             :     {
     606    10275190 :         index_endscan(sysscan->iscan);
     607    10275190 :         index_close(sysscan->irel, AccessShareLock);
     608             :     }
     609             :     else
     610      268012 :         table_endscan(sysscan->scan);
     611             : 
     612    10543202 :     if (sysscan->snapshot)
     613     9573022 :         UnregisterSnapshot(sysscan->snapshot);
     614             : 
     615             :     /*
     616             :      * Reset the bsysscan flag at the end of the systable scan.  See detailed
     617             :      * comments in xact.c where these variables are declared.
     618             :      */
     619    10543202 :     if (TransactionIdIsValid(CheckXidAlive))
     620        1494 :         bsysscan = false;
     621             : 
     622    10543202 :     pfree(sysscan);
     623    10543202 : }
     624             : 
     625             : 
     626             : /*
     627             :  * systable_beginscan_ordered --- set up for ordered catalog scan
     628             :  *
     629             :  * These routines have essentially the same API as systable_beginscan etc,
     630             :  * except that they guarantee to return multiple matching tuples in
     631             :  * index order.  Also, for largely historical reasons, the index to use
     632             :  * is opened and locked by the caller, not here.
     633             :  *
     634             :  * Currently we do not support non-index-based scans here.  (In principle
     635             :  * we could do a heapscan and sort, but the uses are in places that
     636             :  * probably don't need to still work with corrupted catalog indexes.)
     637             :  * For the moment, therefore, these functions are merely the thinest of
     638             :  * wrappers around index_beginscan/index_getnext_slot.  The main reason for
     639             :  * their existence is to centralize possible future support of lossy operators
     640             :  * in catalog scans.
     641             :  */
     642             : SysScanDesc
     643       52420 : systable_beginscan_ordered(Relation heapRelation,
     644             :                            Relation indexRelation,
     645             :                            Snapshot snapshot,
     646             :                            int nkeys, ScanKey key)
     647             : {
     648             :     SysScanDesc sysscan;
     649             :     int         i;
     650             : 
     651             :     /* REINDEX can probably be a hard error here ... */
     652       52420 :     if (ReindexIsProcessingIndex(RelationGetRelid(indexRelation)))
     653           0 :         ereport(ERROR,
     654             :                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
     655             :                  errmsg("cannot access index \"%s\" while it is being reindexed",
     656             :                         RelationGetRelationName(indexRelation))));
     657             :     /* ... but we only throw a warning about violating IgnoreSystemIndexes */
     658       52420 :     if (IgnoreSystemIndexes)
     659           0 :         elog(WARNING, "using index \"%s\" despite IgnoreSystemIndexes",
     660             :              RelationGetRelationName(indexRelation));
     661             : 
     662       52420 :     sysscan = (SysScanDesc) palloc(sizeof(SysScanDescData));
     663             : 
     664       52420 :     sysscan->heap_rel = heapRelation;
     665       52420 :     sysscan->irel = indexRelation;
     666       52420 :     sysscan->slot = table_slot_create(heapRelation, NULL);
     667             : 
     668       52420 :     if (snapshot == NULL)
     669             :     {
     670        7934 :         Oid         relid = RelationGetRelid(heapRelation);
     671             : 
     672        7934 :         snapshot = RegisterSnapshot(GetCatalogSnapshot(relid));
     673        7934 :         sysscan->snapshot = snapshot;
     674             :     }
     675             :     else
     676             :     {
     677             :         /* Caller is responsible for any snapshot. */
     678       44486 :         sysscan->snapshot = NULL;
     679             :     }
     680             : 
     681             :     /* Change attribute numbers to be index column numbers. */
     682      101996 :     for (i = 0; i < nkeys; i++)
     683             :     {
     684             :         int         j;
     685             : 
     686       52806 :         for (j = 0; j < IndexRelationGetNumberOfAttributes(indexRelation); j++)
     687             :         {
     688       52806 :             if (key[i].sk_attno == indexRelation->rd_index->indkey.values[j])
     689             :             {
     690       49576 :                 key[i].sk_attno = j + 1;
     691       49576 :                 break;
     692             :             }
     693             :         }
     694       49576 :         if (j == IndexRelationGetNumberOfAttributes(indexRelation))
     695           0 :             elog(ERROR, "column is not in index");
     696             :     }
     697             : 
     698       52420 :     sysscan->iscan = index_beginscan(heapRelation, indexRelation,
     699             :                                      snapshot, nkeys, 0);
     700       52420 :     index_rescan(sysscan->iscan, key, nkeys, NULL, 0);
     701       52420 :     sysscan->scan = NULL;
     702             : 
     703       52420 :     return sysscan;
     704             : }
     705             : 
     706             : /*
     707             :  * systable_getnext_ordered --- get next tuple in an ordered catalog scan
     708             :  */
     709             : HeapTuple
     710      209466 : systable_getnext_ordered(SysScanDesc sysscan, ScanDirection direction)
     711             : {
     712      209466 :     HeapTuple   htup = NULL;
     713             : 
     714             :     Assert(sysscan->irel);
     715      209466 :     if (index_getnext_slot(sysscan->iscan, direction, sysscan->slot))
     716      158276 :         htup = ExecFetchSlotHeapTuple(sysscan->slot, false, NULL);
     717             : 
     718             :     /* See notes in systable_getnext */
     719      209460 :     if (htup && sysscan->iscan->xs_recheck)
     720           0 :         elog(ERROR, "system catalog scans with lossy index conditions are not implemented");
     721             : 
     722             :     /*
     723             :      * Handle the concurrent abort while fetching the catalog tuple during
     724             :      * logical streaming of a transaction.
     725             :      */
     726      209460 :     HandleConcurrentAbort();
     727             : 
     728      209460 :     return htup;
     729             : }
     730             : 
     731             : /*
     732             :  * systable_endscan_ordered --- close scan, release resources
     733             :  */
     734             : void
     735       52402 : systable_endscan_ordered(SysScanDesc sysscan)
     736             : {
     737       52402 :     if (sysscan->slot)
     738             :     {
     739       52402 :         ExecDropSingleTupleTableSlot(sysscan->slot);
     740       52402 :         sysscan->slot = NULL;
     741             :     }
     742             : 
     743             :     Assert(sysscan->irel);
     744       52402 :     index_endscan(sysscan->iscan);
     745       52402 :     if (sysscan->snapshot)
     746        7922 :         UnregisterSnapshot(sysscan->snapshot);
     747       52402 :     pfree(sysscan);
     748       52402 : }

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