LCOV - code coverage report
Current view: top level - contrib/pgstattuple - pgstattuple.c (source / functions) Hit Total Coverage
Test: PostgreSQL 18devel Lines: 74 186 39.8 %
Date: 2025-04-01 15:15:16 Functions: 10 17 58.8 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : /*
       2             :  * contrib/pgstattuple/pgstattuple.c
       3             :  *
       4             :  * Copyright (c) 2001,2002  Tatsuo Ishii
       5             :  *
       6             :  * Permission to use, copy, modify, and distribute this software and
       7             :  * its documentation for any purpose, without fee, and without a
       8             :  * written agreement is hereby granted, provided that the above
       9             :  * copyright notice and this paragraph and the following two
      10             :  * paragraphs appear in all copies.
      11             :  *
      12             :  * IN NO EVENT SHALL THE AUTHOR BE LIABLE TO ANY PARTY FOR DIRECT,
      13             :  * INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
      14             :  * LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
      15             :  * DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED
      16             :  * OF THE POSSIBILITY OF SUCH DAMAGE.
      17             :  *
      18             :  * THE AUTHOR SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT
      19             :  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
      20             :  * A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS
      21             :  * IS" BASIS, AND THE AUTHOR HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE,
      22             :  * SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
      23             :  */
      24             : 
      25             : #include "postgres.h"
      26             : 
      27             : #include "access/gist_private.h"
      28             : #include "access/hash.h"
      29             : #include "access/heapam.h"
      30             : #include "access/nbtree.h"
      31             : #include "access/relscan.h"
      32             : #include "access/tableam.h"
      33             : #include "catalog/namespace.h"
      34             : #include "catalog/pg_am_d.h"
      35             : #include "funcapi.h"
      36             : #include "miscadmin.h"
      37             : #include "storage/bufmgr.h"
      38             : #include "storage/lmgr.h"
      39             : #include "utils/varlena.h"
      40             : 
      41           2 : PG_MODULE_MAGIC_EXT(
      42             :                     .name = "pgstattuple",
      43             :                     .version = PG_VERSION
      44             : );
      45             : 
      46           2 : PG_FUNCTION_INFO_V1(pgstattuple);
      47           4 : PG_FUNCTION_INFO_V1(pgstattuple_v1_5);
      48           2 : PG_FUNCTION_INFO_V1(pgstattuplebyid);
      49           4 : PG_FUNCTION_INFO_V1(pgstattuplebyid_v1_5);
      50             : 
      51             : /*
      52             :  * struct pgstattuple_type
      53             :  *
      54             :  * tuple_percent, dead_tuple_percent and free_percent are computable,
      55             :  * so not defined here.
      56             :  */
      57             : typedef struct pgstattuple_type
      58             : {
      59             :     uint64      table_len;
      60             :     uint64      tuple_count;
      61             :     uint64      tuple_len;
      62             :     uint64      dead_tuple_count;
      63             :     uint64      dead_tuple_len;
      64             :     uint64      free_space;     /* free/reusable space in bytes */
      65             : } pgstattuple_type;
      66             : 
      67             : typedef void (*pgstat_page) (pgstattuple_type *, Relation, BlockNumber,
      68             :                              BufferAccessStrategy);
      69             : 
      70             : static Datum build_pgstattuple_type(pgstattuple_type *stat,
      71             :                                     FunctionCallInfo fcinfo);
      72             : static Datum pgstat_relation(Relation rel, FunctionCallInfo fcinfo);
      73             : static Datum pgstat_heap(Relation rel, FunctionCallInfo fcinfo);
      74             : static void pgstat_btree_page(pgstattuple_type *stat,
      75             :                               Relation rel, BlockNumber blkno,
      76             :                               BufferAccessStrategy bstrategy);
      77             : static void pgstat_hash_page(pgstattuple_type *stat,
      78             :                              Relation rel, BlockNumber blkno,
      79             :                              BufferAccessStrategy bstrategy);
      80             : static void pgstat_gist_page(pgstattuple_type *stat,
      81             :                              Relation rel, BlockNumber blkno,
      82             :                              BufferAccessStrategy bstrategy);
      83             : static Datum pgstat_index(Relation rel, BlockNumber start,
      84             :                           pgstat_page pagefn, FunctionCallInfo fcinfo);
      85             : static void pgstat_index_page(pgstattuple_type *stat, Page page,
      86             :                               OffsetNumber minoff, OffsetNumber maxoff);
      87             : 
      88             : /*
      89             :  * build_pgstattuple_type -- build a pgstattuple_type tuple
      90             :  */
      91             : static Datum
      92          18 : build_pgstattuple_type(pgstattuple_type *stat, FunctionCallInfo fcinfo)
      93             : {
      94             : #define NCOLUMNS    9
      95             : #define NCHARS      314
      96             : 
      97             :     HeapTuple   tuple;
      98             :     char       *values[NCOLUMNS];
      99             :     char        values_buf[NCOLUMNS][NCHARS];
     100             :     int         i;
     101             :     double      tuple_percent;
     102             :     double      dead_tuple_percent;
     103             :     double      free_percent;   /* free/reusable space in % */
     104             :     TupleDesc   tupdesc;
     105             :     AttInMetadata *attinmeta;
     106             : 
     107             :     /* Build a tuple descriptor for our result type */
     108          18 :     if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
     109           0 :         elog(ERROR, "return type must be a row type");
     110             : 
     111             :     /*
     112             :      * Generate attribute metadata needed later to produce tuples from raw C
     113             :      * strings
     114             :      */
     115          18 :     attinmeta = TupleDescGetAttInMetadata(tupdesc);
     116             : 
     117          18 :     if (stat->table_len == 0)
     118             :     {
     119          16 :         tuple_percent = 0.0;
     120          16 :         dead_tuple_percent = 0.0;
     121          16 :         free_percent = 0.0;
     122             :     }
     123             :     else
     124             :     {
     125           2 :         tuple_percent = 100.0 * stat->tuple_len / stat->table_len;
     126           2 :         dead_tuple_percent = 100.0 * stat->dead_tuple_len / stat->table_len;
     127           2 :         free_percent = 100.0 * stat->free_space / stat->table_len;
     128             :     }
     129             : 
     130             :     /*
     131             :      * Prepare a values array for constructing the tuple. This should be an
     132             :      * array of C strings which will be processed later by the appropriate
     133             :      * "in" functions.
     134             :      */
     135         180 :     for (i = 0; i < NCOLUMNS; i++)
     136         162 :         values[i] = values_buf[i];
     137          18 :     i = 0;
     138          18 :     snprintf(values[i++], NCHARS, INT64_FORMAT, stat->table_len);
     139          18 :     snprintf(values[i++], NCHARS, INT64_FORMAT, stat->tuple_count);
     140          18 :     snprintf(values[i++], NCHARS, INT64_FORMAT, stat->tuple_len);
     141          18 :     snprintf(values[i++], NCHARS, "%.2f", tuple_percent);
     142          18 :     snprintf(values[i++], NCHARS, INT64_FORMAT, stat->dead_tuple_count);
     143          18 :     snprintf(values[i++], NCHARS, INT64_FORMAT, stat->dead_tuple_len);
     144          18 :     snprintf(values[i++], NCHARS, "%.2f", dead_tuple_percent);
     145          18 :     snprintf(values[i++], NCHARS, INT64_FORMAT, stat->free_space);
     146          18 :     snprintf(values[i++], NCHARS, "%.2f", free_percent);
     147             : 
     148             :     /* build a tuple */
     149          18 :     tuple = BuildTupleFromCStrings(attinmeta, values);
     150             : 
     151             :     /* make the tuple into a datum */
     152          18 :     return HeapTupleGetDatum(tuple);
     153             : }
     154             : 
     155             : /* ----------
     156             :  * pgstattuple:
     157             :  * returns live/dead tuples info
     158             :  *
     159             :  * C FUNCTION definition
     160             :  * pgstattuple(text) returns pgstattuple_type
     161             :  *
     162             :  * The superuser() check here must be kept as the library might be upgraded
     163             :  * without the extension being upgraded, meaning that in pre-1.5 installations
     164             :  * these functions could be called by any user.
     165             :  * ----------
     166             :  */
     167             : 
     168             : Datum
     169           0 : pgstattuple(PG_FUNCTION_ARGS)
     170             : {
     171           0 :     text       *relname = PG_GETARG_TEXT_PP(0);
     172             :     RangeVar   *relrv;
     173             :     Relation    rel;
     174             : 
     175           0 :     if (!superuser())
     176           0 :         ereport(ERROR,
     177             :                 (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
     178             :                  errmsg("must be superuser to use pgstattuple functions")));
     179             : 
     180             :     /* open relation */
     181           0 :     relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
     182           0 :     rel = relation_openrv(relrv, AccessShareLock);
     183             : 
     184           0 :     PG_RETURN_DATUM(pgstat_relation(rel, fcinfo));
     185             : }
     186             : 
     187             : /*
     188             :  * As of pgstattuple version 1.5, we no longer need to check if the user
     189             :  * is a superuser because we REVOKE EXECUTE on the function from PUBLIC.
     190             :  * Users can then grant access to it based on their policies.
     191             :  *
     192             :  * Otherwise identical to pgstattuple (above).
     193             :  */
     194             : Datum
     195          20 : pgstattuple_v1_5(PG_FUNCTION_ARGS)
     196             : {
     197          20 :     text       *relname = PG_GETARG_TEXT_PP(0);
     198             :     RangeVar   *relrv;
     199             :     Relation    rel;
     200             : 
     201             :     /* open relation */
     202          20 :     relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
     203          20 :     rel = relation_openrv(relrv, AccessShareLock);
     204             : 
     205          20 :     PG_RETURN_DATUM(pgstat_relation(rel, fcinfo));
     206             : }
     207             : 
     208             : /* Must keep superuser() check, see above. */
     209             : Datum
     210           0 : pgstattuplebyid(PG_FUNCTION_ARGS)
     211             : {
     212           0 :     Oid         relid = PG_GETARG_OID(0);
     213             :     Relation    rel;
     214             : 
     215           0 :     if (!superuser())
     216           0 :         ereport(ERROR,
     217             :                 (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
     218             :                  errmsg("must be superuser to use pgstattuple functions")));
     219             : 
     220             :     /* open relation */
     221           0 :     rel = relation_open(relid, AccessShareLock);
     222             : 
     223           0 :     PG_RETURN_DATUM(pgstat_relation(rel, fcinfo));
     224             : }
     225             : 
     226             : /* Remove superuser() check for 1.5 version, see above */
     227             : Datum
     228           6 : pgstattuplebyid_v1_5(PG_FUNCTION_ARGS)
     229             : {
     230           6 :     Oid         relid = PG_GETARG_OID(0);
     231             :     Relation    rel;
     232             : 
     233             :     /* open relation */
     234           6 :     rel = relation_open(relid, AccessShareLock);
     235             : 
     236           6 :     PG_RETURN_DATUM(pgstat_relation(rel, fcinfo));
     237             : }
     238             : 
     239             : /*
     240             :  * pgstat_relation
     241             :  */
     242             : static Datum
     243          26 : pgstat_relation(Relation rel, FunctionCallInfo fcinfo)
     244             : {
     245             :     const char *err;
     246             : 
     247             :     /*
     248             :      * Reject attempts to read non-local temporary relations; we would be
     249             :      * likely to get wrong data since we have no visibility into the owning
     250             :      * session's local buffers.
     251             :      */
     252          26 :     if (RELATION_IS_OTHER_TEMP(rel))
     253           0 :         ereport(ERROR,
     254             :                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
     255             :                  errmsg("cannot access temporary tables of other sessions")));
     256             : 
     257          26 :     if (RELKIND_HAS_TABLE_AM(rel->rd_rel->relkind) ||
     258          10 :         rel->rd_rel->relkind == RELKIND_SEQUENCE)
     259             :     {
     260          18 :         return pgstat_heap(rel, fcinfo);
     261             :     }
     262           8 :     else if (rel->rd_rel->relkind == RELKIND_INDEX)
     263             :     {
     264             :         /* see pgstatindex_impl */
     265           0 :         if (!rel->rd_index->indisvalid)
     266           0 :             ereport(ERROR,
     267             :                     (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
     268             :                      errmsg("index \"%s\" is not valid",
     269             :                             RelationGetRelationName(rel))));
     270             : 
     271           0 :         switch (rel->rd_rel->relam)
     272             :         {
     273           0 :             case BTREE_AM_OID:
     274           0 :                 return pgstat_index(rel, BTREE_METAPAGE + 1,
     275             :                                     pgstat_btree_page, fcinfo);
     276           0 :             case HASH_AM_OID:
     277           0 :                 return pgstat_index(rel, HASH_METAPAGE + 1,
     278             :                                     pgstat_hash_page, fcinfo);
     279           0 :             case GIST_AM_OID:
     280           0 :                 return pgstat_index(rel, GIST_ROOT_BLKNO + 1,
     281             :                                     pgstat_gist_page, fcinfo);
     282           0 :             case GIN_AM_OID:
     283           0 :                 err = "gin index";
     284           0 :                 break;
     285           0 :             case SPGIST_AM_OID:
     286           0 :                 err = "spgist index";
     287           0 :                 break;
     288           0 :             case BRIN_AM_OID:
     289           0 :                 err = "brin index";
     290           0 :                 break;
     291           0 :             default:
     292           0 :                 err = "unknown index";
     293           0 :                 break;
     294             :         }
     295           0 :         ereport(ERROR,
     296             :                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
     297             :                  errmsg("index \"%s\" (%s) is not supported",
     298             :                         RelationGetRelationName(rel), err)));
     299             :     }
     300             :     else
     301             :     {
     302           8 :         ereport(ERROR,
     303             :                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
     304             :                  errmsg("cannot get tuple-level statistics for relation \"%s\"",
     305             :                         RelationGetRelationName(rel)),
     306             :                  errdetail_relkind_not_supported(rel->rd_rel->relkind)));
     307             :     }
     308             : 
     309             :     return 0;                   /* should not happen */
     310             : }
     311             : 
     312             : /*
     313             :  * pgstat_heap -- returns live/dead tuples info in a heap
     314             :  */
     315             : static Datum
     316          18 : pgstat_heap(Relation rel, FunctionCallInfo fcinfo)
     317             : {
     318             :     TableScanDesc scan;
     319             :     HeapScanDesc hscan;
     320             :     HeapTuple   tuple;
     321             :     BlockNumber nblocks;
     322          18 :     BlockNumber block = 0;      /* next block to count free space in */
     323             :     BlockNumber tupblock;
     324             :     Buffer      buffer;
     325          18 :     pgstattuple_type stat = {0};
     326             :     SnapshotData SnapshotDirty;
     327             : 
     328             :     /*
     329             :      * Sequences always use heap AM, but they don't show that in the catalogs.
     330             :      */
     331          18 :     if (rel->rd_rel->relkind != RELKIND_SEQUENCE &&
     332          16 :         rel->rd_rel->relam != HEAP_TABLE_AM_OID)
     333           0 :         ereport(ERROR,
     334             :                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
     335             :                  errmsg("only heap AM is supported")));
     336             : 
     337             :     /* Disable syncscan because we assume we scan from block zero upwards */
     338          18 :     scan = table_beginscan_strat(rel, SnapshotAny, 0, NULL, true, false);
     339          18 :     hscan = (HeapScanDesc) scan;
     340             : 
     341          18 :     InitDirtySnapshot(SnapshotDirty);
     342             : 
     343          18 :     nblocks = hscan->rs_nblocks; /* # blocks to be scanned */
     344             : 
     345             :     /* scan the relation */
     346          20 :     while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
     347             :     {
     348           2 :         CHECK_FOR_INTERRUPTS();
     349             : 
     350             :         /* must hold a buffer lock to call HeapTupleSatisfiesVisibility */
     351           2 :         LockBuffer(hscan->rs_cbuf, BUFFER_LOCK_SHARE);
     352             : 
     353           2 :         if (HeapTupleSatisfiesVisibility(tuple, &SnapshotDirty, hscan->rs_cbuf))
     354             :         {
     355           2 :             stat.tuple_len += tuple->t_len;
     356           2 :             stat.tuple_count++;
     357             :         }
     358             :         else
     359             :         {
     360           0 :             stat.dead_tuple_len += tuple->t_len;
     361           0 :             stat.dead_tuple_count++;
     362             :         }
     363             : 
     364           2 :         LockBuffer(hscan->rs_cbuf, BUFFER_LOCK_UNLOCK);
     365             : 
     366             :         /*
     367             :          * To avoid physically reading the table twice, try to do the
     368             :          * free-space scan in parallel with the heap scan.  However,
     369             :          * heap_getnext may find no tuples on a given page, so we cannot
     370             :          * simply examine the pages returned by the heap scan.
     371             :          */
     372           2 :         tupblock = ItemPointerGetBlockNumber(&tuple->t_self);
     373             : 
     374           4 :         while (block <= tupblock)
     375             :         {
     376           2 :             CHECK_FOR_INTERRUPTS();
     377             : 
     378           2 :             buffer = ReadBufferExtended(rel, MAIN_FORKNUM, block,
     379             :                                         RBM_NORMAL, hscan->rs_strategy);
     380           2 :             LockBuffer(buffer, BUFFER_LOCK_SHARE);
     381           2 :             stat.free_space += PageGetExactFreeSpace((Page) BufferGetPage(buffer));
     382           2 :             UnlockReleaseBuffer(buffer);
     383           2 :             block++;
     384             :         }
     385             :     }
     386             : 
     387          18 :     while (block < nblocks)
     388             :     {
     389           0 :         CHECK_FOR_INTERRUPTS();
     390             : 
     391           0 :         buffer = ReadBufferExtended(rel, MAIN_FORKNUM, block,
     392             :                                     RBM_NORMAL, hscan->rs_strategy);
     393           0 :         LockBuffer(buffer, BUFFER_LOCK_SHARE);
     394           0 :         stat.free_space += PageGetExactFreeSpace((Page) BufferGetPage(buffer));
     395           0 :         UnlockReleaseBuffer(buffer);
     396           0 :         block++;
     397             :     }
     398             : 
     399          18 :     table_endscan(scan);
     400          18 :     relation_close(rel, AccessShareLock);
     401             : 
     402          18 :     stat.table_len = (uint64) nblocks * BLCKSZ;
     403             : 
     404          18 :     return build_pgstattuple_type(&stat, fcinfo);
     405             : }
     406             : 
     407             : /*
     408             :  * pgstat_btree_page -- check tuples in a btree page
     409             :  */
     410             : static void
     411           0 : pgstat_btree_page(pgstattuple_type *stat, Relation rel, BlockNumber blkno,
     412             :                   BufferAccessStrategy bstrategy)
     413             : {
     414             :     Buffer      buf;
     415             :     Page        page;
     416             : 
     417           0 :     buf = ReadBufferExtended(rel, MAIN_FORKNUM, blkno, RBM_NORMAL, bstrategy);
     418           0 :     LockBuffer(buf, BT_READ);
     419           0 :     page = BufferGetPage(buf);
     420             : 
     421             :     /* Page is valid, see what to do with it */
     422           0 :     if (PageIsNew(page))
     423             :     {
     424             :         /* fully empty page */
     425           0 :         stat->free_space += BLCKSZ;
     426             :     }
     427             :     else
     428             :     {
     429             :         BTPageOpaque opaque;
     430             : 
     431           0 :         opaque = BTPageGetOpaque(page);
     432           0 :         if (P_IGNORE(opaque))
     433             :         {
     434             :             /* deleted or half-dead page */
     435           0 :             stat->free_space += BLCKSZ;
     436             :         }
     437           0 :         else if (P_ISLEAF(opaque))
     438             :         {
     439           0 :             pgstat_index_page(stat, page, P_FIRSTDATAKEY(opaque),
     440           0 :                               PageGetMaxOffsetNumber(page));
     441             :         }
     442             :         else
     443             :         {
     444             :             /* internal page */
     445             :         }
     446             :     }
     447             : 
     448           0 :     _bt_relbuf(rel, buf);
     449           0 : }
     450             : 
     451             : /*
     452             :  * pgstat_hash_page -- check tuples in a hash page
     453             :  */
     454             : static void
     455           0 : pgstat_hash_page(pgstattuple_type *stat, Relation rel, BlockNumber blkno,
     456             :                  BufferAccessStrategy bstrategy)
     457             : {
     458             :     Buffer      buf;
     459             :     Page        page;
     460             : 
     461           0 :     buf = _hash_getbuf_with_strategy(rel, blkno, HASH_READ, 0, bstrategy);
     462           0 :     page = BufferGetPage(buf);
     463             : 
     464           0 :     if (PageGetSpecialSize(page) == MAXALIGN(sizeof(HashPageOpaqueData)))
     465             :     {
     466             :         HashPageOpaque opaque;
     467             : 
     468           0 :         opaque = HashPageGetOpaque(page);
     469           0 :         switch (opaque->hasho_flag & LH_PAGE_TYPE)
     470             :         {
     471           0 :             case LH_UNUSED_PAGE:
     472           0 :                 stat->free_space += BLCKSZ;
     473           0 :                 break;
     474           0 :             case LH_BUCKET_PAGE:
     475             :             case LH_OVERFLOW_PAGE:
     476           0 :                 pgstat_index_page(stat, page, FirstOffsetNumber,
     477           0 :                                   PageGetMaxOffsetNumber(page));
     478           0 :                 break;
     479           0 :             case LH_BITMAP_PAGE:
     480             :             case LH_META_PAGE:
     481             :             default:
     482           0 :                 break;
     483             :         }
     484             :     }
     485             :     else
     486             :     {
     487             :         /* maybe corrupted */
     488             :     }
     489             : 
     490           0 :     _hash_relbuf(rel, buf);
     491           0 : }
     492             : 
     493             : /*
     494             :  * pgstat_gist_page -- check tuples in a gist page
     495             :  */
     496             : static void
     497           0 : pgstat_gist_page(pgstattuple_type *stat, Relation rel, BlockNumber blkno,
     498             :                  BufferAccessStrategy bstrategy)
     499             : {
     500             :     Buffer      buf;
     501             :     Page        page;
     502             : 
     503           0 :     buf = ReadBufferExtended(rel, MAIN_FORKNUM, blkno, RBM_NORMAL, bstrategy);
     504           0 :     LockBuffer(buf, GIST_SHARE);
     505           0 :     gistcheckpage(rel, buf);
     506           0 :     page = BufferGetPage(buf);
     507             : 
     508           0 :     if (GistPageIsLeaf(page))
     509             :     {
     510           0 :         pgstat_index_page(stat, page, FirstOffsetNumber,
     511           0 :                           PageGetMaxOffsetNumber(page));
     512             :     }
     513             :     else
     514             :     {
     515             :         /* root or node */
     516             :     }
     517             : 
     518           0 :     UnlockReleaseBuffer(buf);
     519           0 : }
     520             : 
     521             : /*
     522             :  * pgstat_index -- returns live/dead tuples info in a generic index
     523             :  */
     524             : static Datum
     525           0 : pgstat_index(Relation rel, BlockNumber start, pgstat_page pagefn,
     526             :              FunctionCallInfo fcinfo)
     527             : {
     528             :     BlockNumber nblocks;
     529             :     BlockNumber blkno;
     530             :     BufferAccessStrategy bstrategy;
     531           0 :     pgstattuple_type stat = {0};
     532             : 
     533             :     /* prepare access strategy for this index */
     534           0 :     bstrategy = GetAccessStrategy(BAS_BULKREAD);
     535             : 
     536           0 :     blkno = start;
     537             :     for (;;)
     538             :     {
     539             :         /* Get the current relation length */
     540           0 :         LockRelationForExtension(rel, ExclusiveLock);
     541           0 :         nblocks = RelationGetNumberOfBlocks(rel);
     542           0 :         UnlockRelationForExtension(rel, ExclusiveLock);
     543             : 
     544             :         /* Quit if we've scanned the whole relation */
     545           0 :         if (blkno >= nblocks)
     546             :         {
     547           0 :             stat.table_len = (uint64) nblocks * BLCKSZ;
     548             : 
     549           0 :             break;
     550             :         }
     551             : 
     552           0 :         for (; blkno < nblocks; blkno++)
     553             :         {
     554           0 :             CHECK_FOR_INTERRUPTS();
     555             : 
     556           0 :             pagefn(&stat, rel, blkno, bstrategy);
     557             :         }
     558             :     }
     559             : 
     560           0 :     relation_close(rel, AccessShareLock);
     561             : 
     562           0 :     return build_pgstattuple_type(&stat, fcinfo);
     563             : }
     564             : 
     565             : /*
     566             :  * pgstat_index_page -- for generic index page
     567             :  */
     568             : static void
     569           0 : pgstat_index_page(pgstattuple_type *stat, Page page,
     570             :                   OffsetNumber minoff, OffsetNumber maxoff)
     571             : {
     572             :     OffsetNumber i;
     573             : 
     574           0 :     stat->free_space += PageGetExactFreeSpace(page);
     575             : 
     576           0 :     for (i = minoff; i <= maxoff; i = OffsetNumberNext(i))
     577             :     {
     578           0 :         ItemId      itemid = PageGetItemId(page, i);
     579             : 
     580           0 :         if (ItemIdIsDead(itemid))
     581             :         {
     582           0 :             stat->dead_tuple_count++;
     583           0 :             stat->dead_tuple_len += ItemIdGetLength(itemid);
     584             :         }
     585             :         else
     586             :         {
     587           0 :             stat->tuple_count++;
     588           0 :             stat->tuple_len += ItemIdGetLength(itemid);
     589             :         }
     590             :     }
     591           0 : }

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