LCOV - code coverage report
Current view: top level - src/backend/executor - nodeIndexonlyscan.c (source / functions) Hit Total Coverage
Test: PostgreSQL 17devel Lines: 153 169 90.5 %
Date: 2024-03-28 17:11:35 Functions: 12 13 92.3 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * nodeIndexonlyscan.c
       4             :  *    Routines to support index-only scans
       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/executor/nodeIndexonlyscan.c
      12             :  *
      13             :  *-------------------------------------------------------------------------
      14             :  */
      15             : /*
      16             :  * INTERFACE ROUTINES
      17             :  *      ExecIndexOnlyScan           scans an index
      18             :  *      IndexOnlyNext               retrieve next tuple
      19             :  *      ExecInitIndexOnlyScan       creates and initializes state info.
      20             :  *      ExecReScanIndexOnlyScan     rescans the indexed relation.
      21             :  *      ExecEndIndexOnlyScan        releases all storage.
      22             :  *      ExecIndexOnlyMarkPos        marks scan position.
      23             :  *      ExecIndexOnlyRestrPos       restores scan position.
      24             :  *      ExecIndexOnlyScanEstimate   estimates DSM space needed for
      25             :  *                      parallel index-only scan
      26             :  *      ExecIndexOnlyScanInitializeDSM  initialize DSM for parallel
      27             :  *                      index-only scan
      28             :  *      ExecIndexOnlyScanReInitializeDSM    reinitialize DSM for fresh scan
      29             :  *      ExecIndexOnlyScanInitializeWorker attach to DSM info in parallel worker
      30             :  */
      31             : #include "postgres.h"
      32             : 
      33             : #include "access/genam.h"
      34             : #include "access/relscan.h"
      35             : #include "access/tableam.h"
      36             : #include "access/tupdesc.h"
      37             : #include "access/visibilitymap.h"
      38             : #include "executor/executor.h"
      39             : #include "executor/nodeIndexonlyscan.h"
      40             : #include "executor/nodeIndexscan.h"
      41             : #include "miscadmin.h"
      42             : #include "storage/bufmgr.h"
      43             : #include "storage/predicate.h"
      44             : #include "utils/rel.h"
      45             : 
      46             : 
      47             : static TupleTableSlot *IndexOnlyNext(IndexOnlyScanState *node);
      48             : static void StoreIndexTuple(TupleTableSlot *slot, IndexTuple itup,
      49             :                             TupleDesc itupdesc);
      50             : 
      51             : 
      52             : /* ----------------------------------------------------------------
      53             :  *      IndexOnlyNext
      54             :  *
      55             :  *      Retrieve a tuple from the IndexOnlyScan node's index.
      56             :  * ----------------------------------------------------------------
      57             :  */
      58             : static TupleTableSlot *
      59     5110116 : IndexOnlyNext(IndexOnlyScanState *node)
      60             : {
      61             :     EState     *estate;
      62             :     ExprContext *econtext;
      63             :     ScanDirection direction;
      64             :     IndexScanDesc scandesc;
      65             :     TupleTableSlot *slot;
      66             :     ItemPointer tid;
      67             : 
      68             :     /*
      69             :      * extract necessary information from index scan node
      70             :      */
      71     5110116 :     estate = node->ss.ps.state;
      72             : 
      73             :     /*
      74             :      * Determine which direction to scan the index in based on the plan's scan
      75             :      * direction and the current direction of execution.
      76             :      */
      77     5110116 :     direction = ScanDirectionCombine(estate->es_direction,
      78             :                                      ((IndexOnlyScan *) node->ss.ps.plan)->indexorderdir);
      79     5110116 :     scandesc = node->ioss_ScanDesc;
      80     5110116 :     econtext = node->ss.ps.ps_ExprContext;
      81     5110116 :     slot = node->ss.ss_ScanTupleSlot;
      82             : 
      83     5110116 :     if (scandesc == NULL)
      84             :     {
      85             :         /*
      86             :          * We reach here if the index only scan is not parallel, or if we're
      87             :          * serially executing an index only scan that was planned to be
      88             :          * parallel.
      89             :          */
      90        9750 :         scandesc = index_beginscan(node->ss.ss_currentRelation,
      91             :                                    node->ioss_RelationDesc,
      92             :                                    estate->es_snapshot,
      93             :                                    node->ioss_NumScanKeys,
      94             :                                    node->ioss_NumOrderByKeys);
      95             : 
      96        9750 :         node->ioss_ScanDesc = scandesc;
      97             : 
      98             : 
      99             :         /* Set it up for index-only scan */
     100        9750 :         node->ioss_ScanDesc->xs_want_itup = true;
     101        9750 :         node->ioss_VMBuffer = InvalidBuffer;
     102             : 
     103             :         /*
     104             :          * If no run-time keys to calculate or they are ready, go ahead and
     105             :          * pass the scankeys to the index AM.
     106             :          */
     107        9750 :         if (node->ioss_NumRuntimeKeys == 0 || node->ioss_RuntimeKeysReady)
     108        9750 :             index_rescan(scandesc,
     109        9750 :                          node->ioss_ScanKeys,
     110             :                          node->ioss_NumScanKeys,
     111        9750 :                          node->ioss_OrderByKeys,
     112             :                          node->ioss_NumOrderByKeys);
     113             :     }
     114             : 
     115             :     /*
     116             :      * OK, now that we have what we need, fetch the next tuple.
     117             :      */
     118     5235452 :     while ((tid = index_getnext_tid(scandesc, direction)) != NULL)
     119             :     {
     120     5153182 :         bool        tuple_from_heap = false;
     121             : 
     122     5153182 :         CHECK_FOR_INTERRUPTS();
     123             : 
     124             :         /*
     125             :          * We can skip the heap fetch if the TID references a heap page on
     126             :          * which all tuples are known visible to everybody.  In any case,
     127             :          * we'll use the index tuple not the heap tuple as the data source.
     128             :          *
     129             :          * Note on Memory Ordering Effects: visibilitymap_get_status does not
     130             :          * lock the visibility map buffer, and therefore the result we read
     131             :          * here could be slightly stale.  However, it can't be stale enough to
     132             :          * matter.
     133             :          *
     134             :          * We need to detect clearing a VM bit due to an insert right away,
     135             :          * because the tuple is present in the index page but not visible. The
     136             :          * reading of the TID by this scan (using a shared lock on the index
     137             :          * buffer) is serialized with the insert of the TID into the index
     138             :          * (using an exclusive lock on the index buffer). Because the VM bit
     139             :          * is cleared before updating the index, and locking/unlocking of the
     140             :          * index page acts as a full memory barrier, we are sure to see the
     141             :          * cleared bit if we see a recently-inserted TID.
     142             :          *
     143             :          * Deletes do not update the index page (only VACUUM will clear out
     144             :          * the TID), so the clearing of the VM bit by a delete is not
     145             :          * serialized with this test below, and we may see a value that is
     146             :          * significantly stale. However, we don't care about the delete right
     147             :          * away, because the tuple is still visible until the deleting
     148             :          * transaction commits or the statement ends (if it's our
     149             :          * transaction). In either case, the lock on the VM buffer will have
     150             :          * been released (acting as a write barrier) after clearing the bit.
     151             :          * And for us to have a snapshot that includes the deleting
     152             :          * transaction (making the tuple invisible), we must have acquired
     153             :          * ProcArrayLock after that time, acting as a read barrier.
     154             :          *
     155             :          * It's worth going through this complexity to avoid needing to lock
     156             :          * the VM buffer, which could cause significant contention.
     157             :          */
     158     5153182 :         if (!VM_ALL_VISIBLE(scandesc->heapRelation,
     159             :                             ItemPointerGetBlockNumber(tid),
     160             :                             &node->ioss_VMBuffer))
     161             :         {
     162             :             /*
     163             :              * Rats, we have to visit the heap to check visibility.
     164             :              */
     165     1866980 :             InstrCountTuples2(node, 1);
     166     1866980 :             if (!index_fetch_heap(scandesc, node->ioss_TableSlot))
     167      125330 :                 continue;       /* no visible tuple, try next index entry */
     168             : 
     169     1741650 :             ExecClearTuple(node->ioss_TableSlot);
     170             : 
     171             :             /*
     172             :              * Only MVCC snapshots are supported here, so there should be no
     173             :              * need to keep following the HOT chain once a visible entry has
     174             :              * been found.  If we did want to allow that, we'd need to keep
     175             :              * more state to remember not to call index_getnext_tid next time.
     176             :              */
     177     1741650 :             if (scandesc->xs_heap_continue)
     178           0 :                 elog(ERROR, "non-MVCC snapshots are not supported in index-only scans");
     179             : 
     180             :             /*
     181             :              * Note: at this point we are holding a pin on the heap page, as
     182             :              * recorded in scandesc->xs_cbuf.  We could release that pin now,
     183             :              * but it's not clear whether it's a win to do so.  The next index
     184             :              * entry might require a visit to the same heap page.
     185             :              */
     186             : 
     187     1741650 :             tuple_from_heap = true;
     188             :         }
     189             : 
     190             :         /*
     191             :          * Fill the scan tuple slot with data from the index.  This might be
     192             :          * provided in either HeapTuple or IndexTuple format.  Conceivably an
     193             :          * index AM might fill both fields, in which case we prefer the heap
     194             :          * format, since it's probably a bit cheaper to fill a slot from.
     195             :          */
     196     5027852 :         if (scandesc->xs_hitup)
     197             :         {
     198             :             /*
     199             :              * We don't take the trouble to verify that the provided tuple has
     200             :              * exactly the slot's format, but it seems worth doing a quick
     201             :              * check on the number of fields.
     202             :              */
     203             :             Assert(slot->tts_tupleDescriptor->natts ==
     204             :                    scandesc->xs_hitupdesc->natts);
     205     1437684 :             ExecForceStoreHeapTuple(scandesc->xs_hitup, slot, false);
     206             :         }
     207     3590168 :         else if (scandesc->xs_itup)
     208     3590168 :             StoreIndexTuple(slot, scandesc->xs_itup, scandesc->xs_itupdesc);
     209             :         else
     210           0 :             elog(ERROR, "no data returned for index-only scan");
     211             : 
     212             :         /*
     213             :          * If the index was lossy, we have to recheck the index quals.
     214             :          */
     215     5027852 :         if (scandesc->xs_recheck)
     216             :         {
     217          14 :             econtext->ecxt_scantuple = slot;
     218          14 :             if (!ExecQualAndReset(node->recheckqual, econtext))
     219             :             {
     220             :                 /* Fails recheck, so drop it and loop back for another */
     221           6 :                 InstrCountFiltered2(node, 1);
     222           6 :                 continue;
     223             :             }
     224             :         }
     225             : 
     226             :         /*
     227             :          * We don't currently support rechecking ORDER BY distances.  (In
     228             :          * principle, if the index can support retrieval of the originally
     229             :          * indexed value, it should be able to produce an exact distance
     230             :          * calculation too.  So it's not clear that adding code here for
     231             :          * recheck/re-sort would be worth the trouble.  But we should at least
     232             :          * throw an error if someone tries it.)
     233             :          */
     234     5027846 :         if (scandesc->numberOfOrderBys > 0 && scandesc->xs_recheckorderby)
     235           6 :             ereport(ERROR,
     236             :                     (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
     237             :                      errmsg("lossy distance functions are not supported in index-only scans")));
     238             : 
     239             :         /*
     240             :          * If we didn't access the heap, then we'll need to take a predicate
     241             :          * lock explicitly, as if we had.  For now we do that at page level.
     242             :          */
     243     5027840 :         if (!tuple_from_heap)
     244     3286202 :             PredicateLockPage(scandesc->heapRelation,
     245             :                               ItemPointerGetBlockNumber(tid),
     246             :                               estate->es_snapshot);
     247             : 
     248     5027840 :         return slot;
     249             :     }
     250             : 
     251             :     /*
     252             :      * if we get here it means the index scan failed so we are at the end of
     253             :      * the scan..
     254             :      */
     255       82270 :     return ExecClearTuple(slot);
     256             : }
     257             : 
     258             : /*
     259             :  * StoreIndexTuple
     260             :  *      Fill the slot with data from the index tuple.
     261             :  *
     262             :  * At some point this might be generally-useful functionality, but
     263             :  * right now we don't need it elsewhere.
     264             :  */
     265             : static void
     266     3590168 : StoreIndexTuple(TupleTableSlot *slot, IndexTuple itup, TupleDesc itupdesc)
     267             : {
     268             :     /*
     269             :      * Note: we must use the tupdesc supplied by the AM in index_deform_tuple,
     270             :      * not the slot's tupdesc, in case the latter has different datatypes
     271             :      * (this happens for btree name_ops in particular).  They'd better have
     272             :      * the same number of columns though, as well as being datatype-compatible
     273             :      * which is something we can't so easily check.
     274             :      */
     275             :     Assert(slot->tts_tupleDescriptor->natts == itupdesc->natts);
     276             : 
     277     3590168 :     ExecClearTuple(slot);
     278     3590168 :     index_deform_tuple(itup, itupdesc, slot->tts_values, slot->tts_isnull);
     279     3590168 :     ExecStoreVirtualTuple(slot);
     280     3590168 : }
     281             : 
     282             : /*
     283             :  * IndexOnlyRecheck -- access method routine to recheck a tuple in EvalPlanQual
     284             :  *
     285             :  * This can't really happen, since an index can't supply CTID which would
     286             :  * be necessary data for any potential EvalPlanQual target relation.  If it
     287             :  * did happen, the EPQ code would pass us the wrong data, namely a heap
     288             :  * tuple not an index tuple.  So throw an error.
     289             :  */
     290             : static bool
     291           0 : IndexOnlyRecheck(IndexOnlyScanState *node, TupleTableSlot *slot)
     292             : {
     293           0 :     elog(ERROR, "EvalPlanQual recheck is not supported in index-only scans");
     294             :     return false;               /* keep compiler quiet */
     295             : }
     296             : 
     297             : /* ----------------------------------------------------------------
     298             :  *      ExecIndexOnlyScan(node)
     299             :  * ----------------------------------------------------------------
     300             :  */
     301             : static TupleTableSlot *
     302     5109094 : ExecIndexOnlyScan(PlanState *pstate)
     303             : {
     304     5109094 :     IndexOnlyScanState *node = castNode(IndexOnlyScanState, pstate);
     305             : 
     306             :     /*
     307             :      * If we have runtime keys and they've not already been set up, do it now.
     308             :      */
     309     5109094 :     if (node->ioss_NumRuntimeKeys != 0 && !node->ioss_RuntimeKeysReady)
     310         556 :         ExecReScan((PlanState *) node);
     311             : 
     312     5109094 :     return ExecScan(&node->ss,
     313             :                     (ExecScanAccessMtd) IndexOnlyNext,
     314             :                     (ExecScanRecheckMtd) IndexOnlyRecheck);
     315             : }
     316             : 
     317             : /* ----------------------------------------------------------------
     318             :  *      ExecReScanIndexOnlyScan(node)
     319             :  *
     320             :  *      Recalculates the values of any scan keys whose value depends on
     321             :  *      information known at runtime, then rescans the indexed relation.
     322             :  *
     323             :  *      Updating the scan key was formerly done separately in
     324             :  *      ExecUpdateIndexScanKeys. Integrating it into ReScan makes
     325             :  *      rescans of indices and relations/general streams more uniform.
     326             :  * ----------------------------------------------------------------
     327             :  */
     328             : void
     329       95520 : ExecReScanIndexOnlyScan(IndexOnlyScanState *node)
     330             : {
     331             :     /*
     332             :      * If we are doing runtime key calculations (ie, any of the index key
     333             :      * values weren't simple Consts), compute the new key values.  But first,
     334             :      * reset the context so we don't leak memory as each outer tuple is
     335             :      * scanned.  Note this assumes that we will recalculate *all* runtime keys
     336             :      * on each call.
     337             :      */
     338       95520 :     if (node->ioss_NumRuntimeKeys != 0)
     339             :     {
     340       95352 :         ExprContext *econtext = node->ioss_RuntimeContext;
     341             : 
     342       95352 :         ResetExprContext(econtext);
     343       95352 :         ExecIndexEvalRuntimeKeys(econtext,
     344             :                                  node->ioss_RuntimeKeys,
     345             :                                  node->ioss_NumRuntimeKeys);
     346             :     }
     347       95520 :     node->ioss_RuntimeKeysReady = true;
     348             : 
     349             :     /* reset index scan */
     350       95520 :     if (node->ioss_ScanDesc)
     351       93788 :         index_rescan(node->ioss_ScanDesc,
     352       93788 :                      node->ioss_ScanKeys, node->ioss_NumScanKeys,
     353       93788 :                      node->ioss_OrderByKeys, node->ioss_NumOrderByKeys);
     354             : 
     355       95520 :     ExecScanReScan(&node->ss);
     356       95520 : }
     357             : 
     358             : 
     359             : /* ----------------------------------------------------------------
     360             :  *      ExecEndIndexOnlyScan
     361             :  * ----------------------------------------------------------------
     362             :  */
     363             : void
     364       15298 : ExecEndIndexOnlyScan(IndexOnlyScanState *node)
     365             : {
     366             :     Relation    indexRelationDesc;
     367             :     IndexScanDesc indexScanDesc;
     368             : 
     369             :     /*
     370             :      * extract information from the node
     371             :      */
     372       15298 :     indexRelationDesc = node->ioss_RelationDesc;
     373       15298 :     indexScanDesc = node->ioss_ScanDesc;
     374             : 
     375             :     /* Release VM buffer pin, if any. */
     376       15298 :     if (node->ioss_VMBuffer != InvalidBuffer)
     377             :     {
     378        5968 :         ReleaseBuffer(node->ioss_VMBuffer);
     379        5968 :         node->ioss_VMBuffer = InvalidBuffer;
     380             :     }
     381             : 
     382             :     /*
     383             :      * close the index relation (no-op if we didn't open it)
     384             :      */
     385       15298 :     if (indexScanDesc)
     386        9858 :         index_endscan(indexScanDesc);
     387       15298 :     if (indexRelationDesc)
     388       13026 :         index_close(indexRelationDesc, NoLock);
     389       15298 : }
     390             : 
     391             : /* ----------------------------------------------------------------
     392             :  *      ExecIndexOnlyMarkPos
     393             :  *
     394             :  * Note: we assume that no caller attempts to set a mark before having read
     395             :  * at least one tuple.  Otherwise, ioss_ScanDesc might still be NULL.
     396             :  * ----------------------------------------------------------------
     397             :  */
     398             : void
     399      124010 : ExecIndexOnlyMarkPos(IndexOnlyScanState *node)
     400             : {
     401      124010 :     EState     *estate = node->ss.ps.state;
     402      124010 :     EPQState   *epqstate = estate->es_epq_active;
     403             : 
     404      124010 :     if (epqstate != NULL)
     405             :     {
     406             :         /*
     407             :          * We are inside an EvalPlanQual recheck.  If a test tuple exists for
     408             :          * this relation, then we shouldn't access the index at all.  We would
     409             :          * instead need to save, and later restore, the state of the
     410             :          * relsubs_done flag, so that re-fetching the test tuple is possible.
     411             :          * However, given the assumption that no caller sets a mark at the
     412             :          * start of the scan, we can only get here with relsubs_done[i]
     413             :          * already set, and so no state need be saved.
     414             :          */
     415           0 :         Index       scanrelid = ((Scan *) node->ss.ps.plan)->scanrelid;
     416             : 
     417             :         Assert(scanrelid > 0);
     418           0 :         if (epqstate->relsubs_slot[scanrelid - 1] != NULL ||
     419           0 :             epqstate->relsubs_rowmark[scanrelid - 1] != NULL)
     420             :         {
     421             :             /* Verify the claim above */
     422           0 :             if (!epqstate->relsubs_done[scanrelid - 1])
     423           0 :                 elog(ERROR, "unexpected ExecIndexOnlyMarkPos call in EPQ recheck");
     424           0 :             return;
     425             :         }
     426             :     }
     427             : 
     428      124010 :     index_markpos(node->ioss_ScanDesc);
     429             : }
     430             : 
     431             : /* ----------------------------------------------------------------
     432             :  *      ExecIndexOnlyRestrPos
     433             :  * ----------------------------------------------------------------
     434             :  */
     435             : void
     436           6 : ExecIndexOnlyRestrPos(IndexOnlyScanState *node)
     437             : {
     438           6 :     EState     *estate = node->ss.ps.state;
     439           6 :     EPQState   *epqstate = estate->es_epq_active;
     440             : 
     441           6 :     if (estate->es_epq_active != NULL)
     442             :     {
     443             :         /* See comments in ExecIndexMarkPos */
     444           0 :         Index       scanrelid = ((Scan *) node->ss.ps.plan)->scanrelid;
     445             : 
     446             :         Assert(scanrelid > 0);
     447           0 :         if (epqstate->relsubs_slot[scanrelid - 1] != NULL ||
     448           0 :             epqstate->relsubs_rowmark[scanrelid - 1] != NULL)
     449             :         {
     450             :             /* Verify the claim above */
     451           0 :             if (!epqstate->relsubs_done[scanrelid - 1])
     452           0 :                 elog(ERROR, "unexpected ExecIndexOnlyRestrPos call in EPQ recheck");
     453           0 :             return;
     454             :         }
     455             :     }
     456             : 
     457           6 :     index_restrpos(node->ioss_ScanDesc);
     458             : }
     459             : 
     460             : /* ----------------------------------------------------------------
     461             :  *      ExecInitIndexOnlyScan
     462             :  *
     463             :  *      Initializes the index scan's state information, creates
     464             :  *      scan keys, and opens the base and index relations.
     465             :  *
     466             :  *      Note: index scans have 2 sets of state information because
     467             :  *            we have to keep track of the base relation and the
     468             :  *            index relation.
     469             :  * ----------------------------------------------------------------
     470             :  */
     471             : IndexOnlyScanState *
     472       15430 : ExecInitIndexOnlyScan(IndexOnlyScan *node, EState *estate, int eflags)
     473             : {
     474             :     IndexOnlyScanState *indexstate;
     475             :     Relation    currentRelation;
     476             :     LOCKMODE    lockmode;
     477             :     TupleDesc   tupDesc;
     478             : 
     479             :     /*
     480             :      * create state structure
     481             :      */
     482       15430 :     indexstate = makeNode(IndexOnlyScanState);
     483       15430 :     indexstate->ss.ps.plan = (Plan *) node;
     484       15430 :     indexstate->ss.ps.state = estate;
     485       15430 :     indexstate->ss.ps.ExecProcNode = ExecIndexOnlyScan;
     486             : 
     487             :     /*
     488             :      * Miscellaneous initialization
     489             :      *
     490             :      * create expression context for node
     491             :      */
     492       15430 :     ExecAssignExprContext(estate, &indexstate->ss.ps);
     493             : 
     494             :     /*
     495             :      * open the scan relation
     496             :      */
     497       15430 :     currentRelation = ExecOpenScanRelation(estate, node->scan.scanrelid, eflags);
     498             : 
     499       15430 :     indexstate->ss.ss_currentRelation = currentRelation;
     500       15430 :     indexstate->ss.ss_currentScanDesc = NULL;    /* no heap scan here */
     501             : 
     502             :     /*
     503             :      * Build the scan tuple type using the indextlist generated by the
     504             :      * planner.  We use this, rather than the index's physical tuple
     505             :      * descriptor, because the latter contains storage column types not the
     506             :      * types of the original datums.  (It's the AM's responsibility to return
     507             :      * suitable data anyway.)
     508             :      */
     509       15430 :     tupDesc = ExecTypeFromTL(node->indextlist);
     510       15430 :     ExecInitScanTupleSlot(estate, &indexstate->ss, tupDesc,
     511             :                           &TTSOpsVirtual);
     512             : 
     513             :     /*
     514             :      * We need another slot, in a format that's suitable for the table AM, for
     515             :      * when we need to fetch a tuple from the table for rechecking visibility.
     516             :      */
     517       15430 :     indexstate->ioss_TableSlot =
     518       15430 :         ExecAllocTableSlot(&estate->es_tupleTable,
     519             :                            RelationGetDescr(currentRelation),
     520             :                            table_slot_callbacks(currentRelation));
     521             : 
     522             :     /*
     523             :      * Initialize result type and projection info.  The node's targetlist will
     524             :      * contain Vars with varno = INDEX_VAR, referencing the scan tuple.
     525             :      */
     526       15430 :     ExecInitResultTypeTL(&indexstate->ss.ps);
     527       15430 :     ExecAssignScanProjectionInfoWithVarno(&indexstate->ss, INDEX_VAR);
     528             : 
     529             :     /*
     530             :      * initialize child expressions
     531             :      *
     532             :      * Note: we don't initialize all of the indexorderby expression, only the
     533             :      * sub-parts corresponding to runtime keys (see below).
     534             :      */
     535       15430 :     indexstate->ss.ps.qual =
     536       15430 :         ExecInitQual(node->scan.plan.qual, (PlanState *) indexstate);
     537       15430 :     indexstate->recheckqual =
     538       15430 :         ExecInitQual(node->recheckqual, (PlanState *) indexstate);
     539             : 
     540             :     /*
     541             :      * If we are just doing EXPLAIN (ie, aren't going to run the plan), stop
     542             :      * here.  This allows an index-advisor plugin to EXPLAIN a plan containing
     543             :      * references to nonexistent indexes.
     544             :      */
     545       15430 :     if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
     546        2272 :         return indexstate;
     547             : 
     548             :     /* Open the index relation. */
     549       13158 :     lockmode = exec_rt_fetch(node->scan.scanrelid, estate)->rellockmode;
     550       13158 :     indexstate->ioss_RelationDesc = index_open(node->indexid, lockmode);
     551             : 
     552             :     /*
     553             :      * Initialize index-specific scan state
     554             :      */
     555       13158 :     indexstate->ioss_RuntimeKeysReady = false;
     556       13158 :     indexstate->ioss_RuntimeKeys = NULL;
     557       13158 :     indexstate->ioss_NumRuntimeKeys = 0;
     558             : 
     559             :     /*
     560             :      * build the index scan keys from the index qualification
     561             :      */
     562       13158 :     ExecIndexBuildScanKeys((PlanState *) indexstate,
     563             :                            indexstate->ioss_RelationDesc,
     564             :                            node->indexqual,
     565             :                            false,
     566       13158 :                            &indexstate->ioss_ScanKeys,
     567             :                            &indexstate->ioss_NumScanKeys,
     568             :                            &indexstate->ioss_RuntimeKeys,
     569             :                            &indexstate->ioss_NumRuntimeKeys,
     570             :                            NULL,    /* no ArrayKeys */
     571             :                            NULL);
     572             : 
     573             :     /*
     574             :      * any ORDER BY exprs have to be turned into scankeys in the same way
     575             :      */
     576       13158 :     ExecIndexBuildScanKeys((PlanState *) indexstate,
     577             :                            indexstate->ioss_RelationDesc,
     578             :                            node->indexorderby,
     579             :                            true,
     580       13158 :                            &indexstate->ioss_OrderByKeys,
     581             :                            &indexstate->ioss_NumOrderByKeys,
     582             :                            &indexstate->ioss_RuntimeKeys,
     583             :                            &indexstate->ioss_NumRuntimeKeys,
     584             :                            NULL,    /* no ArrayKeys */
     585             :                            NULL);
     586             : 
     587             :     /*
     588             :      * If we have runtime keys, we need an ExprContext to evaluate them. The
     589             :      * node's standard context won't do because we want to reset that context
     590             :      * for every tuple.  So, build another context just like the other one...
     591             :      * -tgl 7/11/00
     592             :      */
     593       13158 :     if (indexstate->ioss_NumRuntimeKeys != 0)
     594             :     {
     595        2210 :         ExprContext *stdecontext = indexstate->ss.ps.ps_ExprContext;
     596             : 
     597        2210 :         ExecAssignExprContext(estate, &indexstate->ss.ps);
     598        2210 :         indexstate->ioss_RuntimeContext = indexstate->ss.ps.ps_ExprContext;
     599        2210 :         indexstate->ss.ps.ps_ExprContext = stdecontext;
     600             :     }
     601             :     else
     602             :     {
     603       10948 :         indexstate->ioss_RuntimeContext = NULL;
     604             :     }
     605             : 
     606             :     /*
     607             :      * all done.
     608             :      */
     609       13158 :     return indexstate;
     610             : }
     611             : 
     612             : /* ----------------------------------------------------------------
     613             :  *      Parallel Index-only Scan Support
     614             :  * ----------------------------------------------------------------
     615             :  */
     616             : 
     617             : /* ----------------------------------------------------------------
     618             :  *      ExecIndexOnlyScanEstimate
     619             :  *
     620             :  *      Compute the amount of space we'll need in the parallel
     621             :  *      query DSM, and inform pcxt->estimator about our needs.
     622             :  * ----------------------------------------------------------------
     623             :  */
     624             : void
     625          40 : ExecIndexOnlyScanEstimate(IndexOnlyScanState *node,
     626             :                           ParallelContext *pcxt)
     627             : {
     628          40 :     EState     *estate = node->ss.ps.state;
     629             : 
     630          40 :     node->ioss_PscanLen = index_parallelscan_estimate(node->ioss_RelationDesc,
     631             :                                                       estate->es_snapshot);
     632          40 :     shm_toc_estimate_chunk(&pcxt->estimator, node->ioss_PscanLen);
     633          40 :     shm_toc_estimate_keys(&pcxt->estimator, 1);
     634          40 : }
     635             : 
     636             : /* ----------------------------------------------------------------
     637             :  *      ExecIndexOnlyScanInitializeDSM
     638             :  *
     639             :  *      Set up a parallel index-only scan descriptor.
     640             :  * ----------------------------------------------------------------
     641             :  */
     642             : void
     643          40 : ExecIndexOnlyScanInitializeDSM(IndexOnlyScanState *node,
     644             :                                ParallelContext *pcxt)
     645             : {
     646          40 :     EState     *estate = node->ss.ps.state;
     647             :     ParallelIndexScanDesc piscan;
     648             : 
     649          40 :     piscan = shm_toc_allocate(pcxt->toc, node->ioss_PscanLen);
     650          40 :     index_parallelscan_initialize(node->ss.ss_currentRelation,
     651             :                                   node->ioss_RelationDesc,
     652             :                                   estate->es_snapshot,
     653             :                                   piscan);
     654          40 :     shm_toc_insert(pcxt->toc, node->ss.ps.plan->plan_node_id, piscan);
     655          40 :     node->ioss_ScanDesc =
     656          40 :         index_beginscan_parallel(node->ss.ss_currentRelation,
     657             :                                  node->ioss_RelationDesc,
     658             :                                  node->ioss_NumScanKeys,
     659             :                                  node->ioss_NumOrderByKeys,
     660             :                                  piscan);
     661          40 :     node->ioss_ScanDesc->xs_want_itup = true;
     662          40 :     node->ioss_VMBuffer = InvalidBuffer;
     663             : 
     664             :     /*
     665             :      * If no run-time keys to calculate or they are ready, go ahead and pass
     666             :      * the scankeys to the index AM.
     667             :      */
     668          40 :     if (node->ioss_NumRuntimeKeys == 0 || node->ioss_RuntimeKeysReady)
     669          40 :         index_rescan(node->ioss_ScanDesc,
     670          40 :                      node->ioss_ScanKeys, node->ioss_NumScanKeys,
     671          40 :                      node->ioss_OrderByKeys, node->ioss_NumOrderByKeys);
     672          40 : }
     673             : 
     674             : /* ----------------------------------------------------------------
     675             :  *      ExecIndexOnlyScanReInitializeDSM
     676             :  *
     677             :  *      Reset shared state before beginning a fresh scan.
     678             :  * ----------------------------------------------------------------
     679             :  */
     680             : void
     681          12 : ExecIndexOnlyScanReInitializeDSM(IndexOnlyScanState *node,
     682             :                                  ParallelContext *pcxt)
     683             : {
     684          12 :     index_parallelrescan(node->ioss_ScanDesc);
     685          12 : }
     686             : 
     687             : /* ----------------------------------------------------------------
     688             :  *      ExecIndexOnlyScanInitializeWorker
     689             :  *
     690             :  *      Copy relevant information from TOC into planstate.
     691             :  * ----------------------------------------------------------------
     692             :  */
     693             : void
     694         200 : ExecIndexOnlyScanInitializeWorker(IndexOnlyScanState *node,
     695             :                                   ParallelWorkerContext *pwcxt)
     696             : {
     697             :     ParallelIndexScanDesc piscan;
     698             : 
     699         200 :     piscan = shm_toc_lookup(pwcxt->toc, node->ss.ps.plan->plan_node_id, false);
     700         200 :     node->ioss_ScanDesc =
     701         200 :         index_beginscan_parallel(node->ss.ss_currentRelation,
     702             :                                  node->ioss_RelationDesc,
     703             :                                  node->ioss_NumScanKeys,
     704             :                                  node->ioss_NumOrderByKeys,
     705             :                                  piscan);
     706         200 :     node->ioss_ScanDesc->xs_want_itup = true;
     707             : 
     708             :     /*
     709             :      * If no run-time keys to calculate or they are ready, go ahead and pass
     710             :      * the scankeys to the index AM.
     711             :      */
     712         200 :     if (node->ioss_NumRuntimeKeys == 0 || node->ioss_RuntimeKeysReady)
     713         200 :         index_rescan(node->ioss_ScanDesc,
     714         200 :                      node->ioss_ScanKeys, node->ioss_NumScanKeys,
     715         200 :                      node->ioss_OrderByKeys, node->ioss_NumOrderByKeys);
     716         200 : }

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