LCOV - code coverage report
Current view: top level - contrib/pgstattuple - pgstatindex.c (source / functions) Hit Total Coverage
Test: PostgreSQL 18devel Lines: 160 235 68.1 %
Date: 2024-12-02 20:15:07 Functions: 21 26 80.8 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : /*
       2             :  * contrib/pgstattuple/pgstatindex.c
       3             :  *
       4             :  *
       5             :  * pgstatindex
       6             :  *
       7             :  * Copyright (c) 2006 Satoshi Nagayasu <nagayasus@nttdata.co.jp>
       8             :  *
       9             :  * Permission to use, copy, modify, and distribute this software and
      10             :  * its documentation for any purpose, without fee, and without a
      11             :  * written agreement is hereby granted, provided that the above
      12             :  * copyright notice and this paragraph and the following two
      13             :  * paragraphs appear in all copies.
      14             :  *
      15             :  * IN NO EVENT SHALL THE AUTHOR BE LIABLE TO ANY PARTY FOR DIRECT,
      16             :  * INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
      17             :  * LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
      18             :  * DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED
      19             :  * OF THE POSSIBILITY OF SUCH DAMAGE.
      20             :  *
      21             :  * THE AUTHOR SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT
      22             :  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
      23             :  * A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS
      24             :  * IS" BASIS, AND THE AUTHOR HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE,
      25             :  * SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
      26             :  */
      27             : 
      28             : #include "postgres.h"
      29             : 
      30             : #include "access/gin_private.h"
      31             : #include "access/hash.h"
      32             : #include "access/htup_details.h"
      33             : #include "access/nbtree.h"
      34             : #include "access/relation.h"
      35             : #include "catalog/namespace.h"
      36             : #include "catalog/pg_am.h"
      37             : #include "funcapi.h"
      38             : #include "miscadmin.h"
      39             : #include "storage/bufmgr.h"
      40             : #include "utils/rel.h"
      41             : #include "utils/varlena.h"
      42             : 
      43             : 
      44             : /*
      45             :  * Because of backward-compatibility issue, we have decided to have
      46             :  * two types of interfaces, with regclass-type input arg and text-type
      47             :  * input arg, for each function.
      48             :  *
      49             :  * Those functions which have text-type input arg will be deprecated
      50             :  * in the future release.
      51             :  */
      52           2 : PG_FUNCTION_INFO_V1(pgstatindex);
      53           2 : PG_FUNCTION_INFO_V1(pgstatindexbyid);
      54           2 : PG_FUNCTION_INFO_V1(pg_relpages);
      55           2 : PG_FUNCTION_INFO_V1(pg_relpagesbyid);
      56           2 : PG_FUNCTION_INFO_V1(pgstatginindex);
      57           4 : PG_FUNCTION_INFO_V1(pgstathashindex);
      58             : 
      59           4 : PG_FUNCTION_INFO_V1(pgstatindex_v1_5);
      60           4 : PG_FUNCTION_INFO_V1(pgstatindexbyid_v1_5);
      61           4 : PG_FUNCTION_INFO_V1(pg_relpages_v1_5);
      62           4 : PG_FUNCTION_INFO_V1(pg_relpagesbyid_v1_5);
      63           4 : PG_FUNCTION_INFO_V1(pgstatginindex_v1_5);
      64             : 
      65             : Datum       pgstatginindex_internal(Oid relid, FunctionCallInfo fcinfo);
      66             : 
      67             : #define IS_INDEX(r) ((r)->rd_rel->relkind == RELKIND_INDEX)
      68             : #define IS_BTREE(r) ((r)->rd_rel->relam == BTREE_AM_OID)
      69             : #define IS_GIN(r) ((r)->rd_rel->relam == GIN_AM_OID)
      70             : #define IS_HASH(r) ((r)->rd_rel->relam == HASH_AM_OID)
      71             : 
      72             : /* ------------------------------------------------
      73             :  * A structure for a whole btree index statistics
      74             :  * used by pgstatindex().
      75             :  * ------------------------------------------------
      76             :  */
      77             : typedef struct BTIndexStat
      78             : {
      79             :     uint32      version;
      80             :     uint32      level;
      81             :     BlockNumber root_blkno;
      82             : 
      83             :     uint64      internal_pages;
      84             :     uint64      leaf_pages;
      85             :     uint64      empty_pages;
      86             :     uint64      deleted_pages;
      87             : 
      88             :     uint64      max_avail;
      89             :     uint64      free_space;
      90             : 
      91             :     uint64      fragments;
      92             : } BTIndexStat;
      93             : 
      94             : /* ------------------------------------------------
      95             :  * A structure for a whole GIN index statistics
      96             :  * used by pgstatginindex().
      97             :  * ------------------------------------------------
      98             :  */
      99             : typedef struct GinIndexStat
     100             : {
     101             :     int32       version;
     102             : 
     103             :     BlockNumber pending_pages;
     104             :     int64       pending_tuples;
     105             : } GinIndexStat;
     106             : 
     107             : /* ------------------------------------------------
     108             :  * A structure for a whole HASH index statistics
     109             :  * used by pgstathashindex().
     110             :  * ------------------------------------------------
     111             :  */
     112             : typedef struct HashIndexStat
     113             : {
     114             :     int32       version;
     115             :     int32       space_per_page;
     116             : 
     117             :     BlockNumber bucket_pages;
     118             :     BlockNumber overflow_pages;
     119             :     BlockNumber bitmap_pages;
     120             :     BlockNumber unused_pages;
     121             : 
     122             :     int64       live_items;
     123             :     int64       dead_items;
     124             :     uint64      free_space;
     125             : } HashIndexStat;
     126             : 
     127             : static Datum pgstatindex_impl(Relation rel, FunctionCallInfo fcinfo);
     128             : static int64 pg_relpages_impl(Relation rel);
     129             : static void GetHashPageStats(Page page, HashIndexStat *stats);
     130             : 
     131             : /* ------------------------------------------------------
     132             :  * pgstatindex()
     133             :  *
     134             :  * Usage: SELECT * FROM pgstatindex('t1_pkey');
     135             :  *
     136             :  * The superuser() check here must be kept as the library might be upgraded
     137             :  * without the extension being upgraded, meaning that in pre-1.5 installations
     138             :  * these functions could be called by any user.
     139             :  * ------------------------------------------------------
     140             :  */
     141             : Datum
     142           0 : pgstatindex(PG_FUNCTION_ARGS)
     143             : {
     144           0 :     text       *relname = PG_GETARG_TEXT_PP(0);
     145             :     Relation    rel;
     146             :     RangeVar   *relrv;
     147             : 
     148           0 :     if (!superuser())
     149           0 :         ereport(ERROR,
     150             :                 (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
     151             :                  errmsg("must be superuser to use pgstattuple functions")));
     152             : 
     153           0 :     relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
     154           0 :     rel = relation_openrv(relrv, AccessShareLock);
     155             : 
     156           0 :     PG_RETURN_DATUM(pgstatindex_impl(rel, fcinfo));
     157             : }
     158             : 
     159             : /*
     160             :  * As of pgstattuple version 1.5, we no longer need to check if the user
     161             :  * is a superuser because we REVOKE EXECUTE on the function from PUBLIC.
     162             :  * Users can then grant access to it based on their policies.
     163             :  *
     164             :  * Otherwise identical to pgstatindex (above).
     165             :  */
     166             : Datum
     167          22 : pgstatindex_v1_5(PG_FUNCTION_ARGS)
     168             : {
     169          22 :     text       *relname = PG_GETARG_TEXT_PP(0);
     170             :     Relation    rel;
     171             :     RangeVar   *relrv;
     172             : 
     173          22 :     relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
     174          22 :     rel = relation_openrv(relrv, AccessShareLock);
     175             : 
     176          22 :     PG_RETURN_DATUM(pgstatindex_impl(rel, fcinfo));
     177             : }
     178             : 
     179             : /*
     180             :  * The superuser() check here must be kept as the library might be upgraded
     181             :  * without the extension being upgraded, meaning that in pre-1.5 installations
     182             :  * these functions could be called by any user.
     183             :  */
     184             : Datum
     185           0 : pgstatindexbyid(PG_FUNCTION_ARGS)
     186             : {
     187           0 :     Oid         relid = PG_GETARG_OID(0);
     188             :     Relation    rel;
     189             : 
     190           0 :     if (!superuser())
     191           0 :         ereport(ERROR,
     192             :                 (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
     193             :                  errmsg("must be superuser to use pgstattuple functions")));
     194             : 
     195           0 :     rel = relation_open(relid, AccessShareLock);
     196             : 
     197           0 :     PG_RETURN_DATUM(pgstatindex_impl(rel, fcinfo));
     198             : }
     199             : 
     200             : /* No need for superuser checks in v1.5, see above */
     201             : Datum
     202           2 : pgstatindexbyid_v1_5(PG_FUNCTION_ARGS)
     203             : {
     204           2 :     Oid         relid = PG_GETARG_OID(0);
     205             :     Relation    rel;
     206             : 
     207           2 :     rel = relation_open(relid, AccessShareLock);
     208             : 
     209           2 :     PG_RETURN_DATUM(pgstatindex_impl(rel, fcinfo));
     210             : }
     211             : 
     212             : static Datum
     213          24 : pgstatindex_impl(Relation rel, FunctionCallInfo fcinfo)
     214             : {
     215             :     Datum       result;
     216             :     BlockNumber nblocks;
     217             :     BlockNumber blkno;
     218             :     BTIndexStat indexStat;
     219          24 :     BufferAccessStrategy bstrategy = GetAccessStrategy(BAS_BULKREAD);
     220             : 
     221          24 :     if (!IS_INDEX(rel) || !IS_BTREE(rel))
     222          14 :         ereport(ERROR,
     223             :                 (errcode(ERRCODE_WRONG_OBJECT_TYPE),
     224             :                  errmsg("relation \"%s\" is not a btree index",
     225             :                         RelationGetRelationName(rel))));
     226             : 
     227             :     /*
     228             :      * Reject attempts to read non-local temporary relations; we would be
     229             :      * likely to get wrong data since we have no visibility into the owning
     230             :      * session's local buffers.
     231             :      */
     232          10 :     if (RELATION_IS_OTHER_TEMP(rel))
     233           0 :         ereport(ERROR,
     234             :                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
     235             :                  errmsg("cannot access temporary tables of other sessions")));
     236             : 
     237             :     /*
     238             :      * A !indisready index could lead to ERRCODE_DATA_CORRUPTED later, so exit
     239             :      * early.  We're capable of assessing an indisready&&!indisvalid index,
     240             :      * but the results could be confusing.  For example, the index's size
     241             :      * could be too low for a valid index of the table.
     242             :      */
     243          10 :     if (!rel->rd_index->indisvalid)
     244           0 :         ereport(ERROR,
     245             :                 (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
     246             :                  errmsg("index \"%s\" is not valid",
     247             :                         RelationGetRelationName(rel))));
     248             : 
     249             :     /*
     250             :      * Read metapage
     251             :      */
     252             :     {
     253          10 :         Buffer      buffer = ReadBufferExtended(rel, MAIN_FORKNUM, 0, RBM_NORMAL, bstrategy);
     254          10 :         Page        page = BufferGetPage(buffer);
     255          10 :         BTMetaPageData *metad = BTPageGetMeta(page);
     256             : 
     257          10 :         indexStat.version = metad->btm_version;
     258          10 :         indexStat.level = metad->btm_level;
     259          10 :         indexStat.root_blkno = metad->btm_root;
     260             : 
     261          10 :         ReleaseBuffer(buffer);
     262             :     }
     263             : 
     264             :     /* -- init counters -- */
     265          10 :     indexStat.internal_pages = 0;
     266          10 :     indexStat.leaf_pages = 0;
     267          10 :     indexStat.empty_pages = 0;
     268          10 :     indexStat.deleted_pages = 0;
     269             : 
     270          10 :     indexStat.max_avail = 0;
     271          10 :     indexStat.free_space = 0;
     272             : 
     273          10 :     indexStat.fragments = 0;
     274             : 
     275             :     /*
     276             :      * Scan all blocks except the metapage
     277             :      */
     278          10 :     nblocks = RelationGetNumberOfBlocks(rel);
     279             : 
     280          10 :     for (blkno = 1; blkno < nblocks; blkno++)
     281             :     {
     282             :         Buffer      buffer;
     283             :         Page        page;
     284             :         BTPageOpaque opaque;
     285             : 
     286           0 :         CHECK_FOR_INTERRUPTS();
     287             : 
     288             :         /* Read and lock buffer */
     289           0 :         buffer = ReadBufferExtended(rel, MAIN_FORKNUM, blkno, RBM_NORMAL, bstrategy);
     290           0 :         LockBuffer(buffer, BUFFER_LOCK_SHARE);
     291             : 
     292           0 :         page = BufferGetPage(buffer);
     293           0 :         opaque = BTPageGetOpaque(page);
     294             : 
     295             :         /*
     296             :          * Determine page type, and update totals.
     297             :          *
     298             :          * Note that we arbitrarily bucket deleted pages together without
     299             :          * considering if they're leaf pages or internal pages.
     300             :          */
     301           0 :         if (P_ISDELETED(opaque))
     302           0 :             indexStat.deleted_pages++;
     303           0 :         else if (P_IGNORE(opaque))
     304           0 :             indexStat.empty_pages++;    /* this is the "half dead" state */
     305           0 :         else if (P_ISLEAF(opaque))
     306             :         {
     307             :             int         max_avail;
     308             : 
     309           0 :             max_avail = BLCKSZ - (BLCKSZ - ((PageHeader) page)->pd_special + SizeOfPageHeaderData);
     310           0 :             indexStat.max_avail += max_avail;
     311           0 :             indexStat.free_space += PageGetExactFreeSpace(page);
     312             : 
     313           0 :             indexStat.leaf_pages++;
     314             : 
     315             :             /*
     316             :              * If the next leaf is on an earlier block, it means a
     317             :              * fragmentation.
     318             :              */
     319           0 :             if (opaque->btpo_next != P_NONE && opaque->btpo_next < blkno)
     320           0 :                 indexStat.fragments++;
     321             :         }
     322             :         else
     323           0 :             indexStat.internal_pages++;
     324             : 
     325             :         /* Unlock and release buffer */
     326           0 :         LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
     327           0 :         ReleaseBuffer(buffer);
     328             :     }
     329             : 
     330          10 :     relation_close(rel, AccessShareLock);
     331             : 
     332             :     /*----------------------------
     333             :      * Build a result tuple
     334             :      *----------------------------
     335             :      */
     336             :     {
     337             :         TupleDesc   tupleDesc;
     338             :         int         j;
     339             :         char       *values[10];
     340             :         HeapTuple   tuple;
     341             : 
     342             :         /* Build a tuple descriptor for our result type */
     343          10 :         if (get_call_result_type(fcinfo, NULL, &tupleDesc) != TYPEFUNC_COMPOSITE)
     344           0 :             elog(ERROR, "return type must be a row type");
     345             : 
     346          10 :         j = 0;
     347          10 :         values[j++] = psprintf("%d", indexStat.version);
     348          10 :         values[j++] = psprintf("%d", indexStat.level);
     349          20 :         values[j++] = psprintf(INT64_FORMAT,
     350             :                                (1 + /* include the metapage in index_size */
     351          10 :                                 indexStat.leaf_pages +
     352          10 :                                 indexStat.internal_pages +
     353          10 :                                 indexStat.deleted_pages +
     354          10 :                                 indexStat.empty_pages) * BLCKSZ);
     355          10 :         values[j++] = psprintf("%u", indexStat.root_blkno);
     356          10 :         values[j++] = psprintf(INT64_FORMAT, indexStat.internal_pages);
     357          10 :         values[j++] = psprintf(INT64_FORMAT, indexStat.leaf_pages);
     358          10 :         values[j++] = psprintf(INT64_FORMAT, indexStat.empty_pages);
     359          10 :         values[j++] = psprintf(INT64_FORMAT, indexStat.deleted_pages);
     360          10 :         if (indexStat.max_avail > 0)
     361           0 :             values[j++] = psprintf("%.2f",
     362           0 :                                    100.0 - (double) indexStat.free_space / (double) indexStat.max_avail * 100.0);
     363             :         else
     364          10 :             values[j++] = pstrdup("NaN");
     365          10 :         if (indexStat.leaf_pages > 0)
     366           0 :             values[j++] = psprintf("%.2f",
     367           0 :                                    (double) indexStat.fragments / (double) indexStat.leaf_pages * 100.0);
     368             :         else
     369          10 :             values[j++] = pstrdup("NaN");
     370             : 
     371          10 :         tuple = BuildTupleFromCStrings(TupleDescGetAttInMetadata(tupleDesc),
     372             :                                        values);
     373             : 
     374          10 :         result = HeapTupleGetDatum(tuple);
     375             :     }
     376             : 
     377          10 :     return result;
     378             : }
     379             : 
     380             : /* --------------------------------------------------------
     381             :  * pg_relpages()
     382             :  *
     383             :  * Get the number of pages of the table/index.
     384             :  *
     385             :  * Usage: SELECT pg_relpages('t1');
     386             :  *        SELECT pg_relpages('t1_pkey');
     387             :  *
     388             :  * Must keep superuser() check, see above.
     389             :  * --------------------------------------------------------
     390             :  */
     391             : Datum
     392           0 : pg_relpages(PG_FUNCTION_ARGS)
     393             : {
     394           0 :     text       *relname = PG_GETARG_TEXT_PP(0);
     395             :     Relation    rel;
     396             :     RangeVar   *relrv;
     397             : 
     398           0 :     if (!superuser())
     399           0 :         ereport(ERROR,
     400             :                 (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
     401             :                  errmsg("must be superuser to use pgstattuple functions")));
     402             : 
     403           0 :     relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
     404           0 :     rel = relation_openrv(relrv, AccessShareLock);
     405             : 
     406           0 :     PG_RETURN_INT64(pg_relpages_impl(rel));
     407             : }
     408             : 
     409             : /* No need for superuser checks in v1.5, see above */
     410             : Datum
     411          20 : pg_relpages_v1_5(PG_FUNCTION_ARGS)
     412             : {
     413          20 :     text       *relname = PG_GETARG_TEXT_PP(0);
     414             :     Relation    rel;
     415             :     RangeVar   *relrv;
     416             : 
     417          20 :     relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
     418          20 :     rel = relation_openrv(relrv, AccessShareLock);
     419             : 
     420          20 :     PG_RETURN_INT64(pg_relpages_impl(rel));
     421             : }
     422             : 
     423             : /* Must keep superuser() check, see above. */
     424             : Datum
     425           0 : pg_relpagesbyid(PG_FUNCTION_ARGS)
     426             : {
     427           0 :     Oid         relid = PG_GETARG_OID(0);
     428             :     Relation    rel;
     429             : 
     430           0 :     if (!superuser())
     431           0 :         ereport(ERROR,
     432             :                 (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
     433             :                  errmsg("must be superuser to use pgstattuple functions")));
     434             : 
     435           0 :     rel = relation_open(relid, AccessShareLock);
     436             : 
     437           0 :     PG_RETURN_INT64(pg_relpages_impl(rel));
     438             : }
     439             : 
     440             : /* No need for superuser checks in v1.5, see above */
     441             : Datum
     442           6 : pg_relpagesbyid_v1_5(PG_FUNCTION_ARGS)
     443             : {
     444           6 :     Oid         relid = PG_GETARG_OID(0);
     445             :     Relation    rel;
     446             : 
     447           6 :     rel = relation_open(relid, AccessShareLock);
     448             : 
     449           6 :     PG_RETURN_INT64(pg_relpages_impl(rel));
     450             : }
     451             : 
     452             : static int64
     453          26 : pg_relpages_impl(Relation rel)
     454             : {
     455             :     int64       relpages;
     456             : 
     457          26 :     if (!RELKIND_HAS_STORAGE(rel->rd_rel->relkind))
     458           6 :         ereport(ERROR,
     459             :                 (errcode(ERRCODE_WRONG_OBJECT_TYPE),
     460             :                  errmsg("cannot get page count of relation \"%s\"",
     461             :                         RelationGetRelationName(rel)),
     462             :                  errdetail_relkind_not_supported(rel->rd_rel->relkind)));
     463             : 
     464             :     /* note: this will work OK on non-local temp tables */
     465             : 
     466          20 :     relpages = RelationGetNumberOfBlocks(rel);
     467             : 
     468          20 :     relation_close(rel, AccessShareLock);
     469             : 
     470          20 :     return relpages;
     471             : }
     472             : 
     473             : /* ------------------------------------------------------
     474             :  * pgstatginindex()
     475             :  *
     476             :  * Usage: SELECT * FROM pgstatginindex('ginindex');
     477             :  *
     478             :  * Must keep superuser() check, see above.
     479             :  * ------------------------------------------------------
     480             :  */
     481             : Datum
     482           0 : pgstatginindex(PG_FUNCTION_ARGS)
     483             : {
     484           0 :     Oid         relid = PG_GETARG_OID(0);
     485             : 
     486           0 :     if (!superuser())
     487           0 :         ereport(ERROR,
     488             :                 (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
     489             :                  errmsg("must be superuser to use pgstattuple functions")));
     490             : 
     491           0 :     PG_RETURN_DATUM(pgstatginindex_internal(relid, fcinfo));
     492             : }
     493             : 
     494             : /* No need for superuser checks in v1.5, see above */
     495             : Datum
     496          16 : pgstatginindex_v1_5(PG_FUNCTION_ARGS)
     497             : {
     498          16 :     Oid         relid = PG_GETARG_OID(0);
     499             : 
     500          16 :     PG_RETURN_DATUM(pgstatginindex_internal(relid, fcinfo));
     501             : }
     502             : 
     503             : Datum
     504          16 : pgstatginindex_internal(Oid relid, FunctionCallInfo fcinfo)
     505             : {
     506             :     Relation    rel;
     507             :     Buffer      buffer;
     508             :     Page        page;
     509             :     GinMetaPageData *metadata;
     510             :     GinIndexStat stats;
     511             :     HeapTuple   tuple;
     512             :     TupleDesc   tupleDesc;
     513             :     Datum       values[3];
     514          16 :     bool        nulls[3] = {false, false, false};
     515             :     Datum       result;
     516             : 
     517          16 :     rel = relation_open(relid, AccessShareLock);
     518             : 
     519          16 :     if (!IS_INDEX(rel) || !IS_GIN(rel))
     520          14 :         ereport(ERROR,
     521             :                 (errcode(ERRCODE_WRONG_OBJECT_TYPE),
     522             :                  errmsg("relation \"%s\" is not a GIN index",
     523             :                         RelationGetRelationName(rel))));
     524             : 
     525             :     /*
     526             :      * Reject attempts to read non-local temporary relations; we would be
     527             :      * likely to get wrong data since we have no visibility into the owning
     528             :      * session's local buffers.
     529             :      */
     530           2 :     if (RELATION_IS_OTHER_TEMP(rel))
     531           0 :         ereport(ERROR,
     532             :                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
     533             :                  errmsg("cannot access temporary indexes of other sessions")));
     534             : 
     535             :     /* see pgstatindex_impl */
     536           2 :     if (!rel->rd_index->indisvalid)
     537           0 :         ereport(ERROR,
     538             :                 (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
     539             :                  errmsg("index \"%s\" is not valid",
     540             :                         RelationGetRelationName(rel))));
     541             : 
     542             :     /*
     543             :      * Read metapage
     544             :      */
     545           2 :     buffer = ReadBuffer(rel, GIN_METAPAGE_BLKNO);
     546           2 :     LockBuffer(buffer, GIN_SHARE);
     547           2 :     page = BufferGetPage(buffer);
     548           2 :     metadata = GinPageGetMeta(page);
     549             : 
     550           2 :     stats.version = metadata->ginVersion;
     551           2 :     stats.pending_pages = metadata->nPendingPages;
     552           2 :     stats.pending_tuples = metadata->nPendingHeapTuples;
     553             : 
     554           2 :     UnlockReleaseBuffer(buffer);
     555           2 :     relation_close(rel, AccessShareLock);
     556             : 
     557             :     /*
     558             :      * Build a tuple descriptor for our result type
     559             :      */
     560           2 :     if (get_call_result_type(fcinfo, NULL, &tupleDesc) != TYPEFUNC_COMPOSITE)
     561           0 :         elog(ERROR, "return type must be a row type");
     562             : 
     563           2 :     values[0] = Int32GetDatum(stats.version);
     564           2 :     values[1] = UInt32GetDatum(stats.pending_pages);
     565           2 :     values[2] = Int64GetDatum(stats.pending_tuples);
     566             : 
     567             :     /*
     568             :      * Build and return the tuple
     569             :      */
     570           2 :     tuple = heap_form_tuple(tupleDesc, values, nulls);
     571           2 :     result = HeapTupleGetDatum(tuple);
     572             : 
     573           2 :     return result;
     574             : }
     575             : 
     576             : /* ------------------------------------------------------
     577             :  * pgstathashindex()
     578             :  *
     579             :  * Usage: SELECT * FROM pgstathashindex('hashindex');
     580             :  * ------------------------------------------------------
     581             :  */
     582             : Datum
     583          20 : pgstathashindex(PG_FUNCTION_ARGS)
     584             : {
     585          20 :     Oid         relid = PG_GETARG_OID(0);
     586             :     BlockNumber nblocks;
     587             :     BlockNumber blkno;
     588             :     Relation    rel;
     589             :     HashIndexStat stats;
     590             :     BufferAccessStrategy bstrategy;
     591             :     HeapTuple   tuple;
     592             :     TupleDesc   tupleDesc;
     593             :     Datum       values[8];
     594          20 :     bool        nulls[8] = {0};
     595             :     Buffer      metabuf;
     596             :     HashMetaPage metap;
     597             :     float8      free_percent;
     598             :     uint64      total_space;
     599             : 
     600          20 :     rel = relation_open(relid, AccessShareLock);
     601             : 
     602          20 :     if (!IS_INDEX(rel) || !IS_HASH(rel))
     603          16 :         ereport(ERROR,
     604             :                 (errcode(ERRCODE_WRONG_OBJECT_TYPE),
     605             :                  errmsg("relation \"%s\" is not a hash index",
     606             :                         RelationGetRelationName(rel))));
     607             : 
     608             :     /*
     609             :      * Reject attempts to read non-local temporary relations; we would be
     610             :      * likely to get wrong data since we have no visibility into the owning
     611             :      * session's local buffers.
     612             :      */
     613           4 :     if (RELATION_IS_OTHER_TEMP(rel))
     614           0 :         ereport(ERROR,
     615             :                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
     616             :                  errmsg("cannot access temporary indexes of other sessions")));
     617             : 
     618             :     /* see pgstatindex_impl */
     619           4 :     if (!rel->rd_index->indisvalid)
     620           0 :         ereport(ERROR,
     621             :                 (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
     622             :                  errmsg("index \"%s\" is not valid",
     623             :                         RelationGetRelationName(rel))));
     624             : 
     625             :     /* Get the information we need from the metapage. */
     626           4 :     memset(&stats, 0, sizeof(stats));
     627           4 :     metabuf = _hash_getbuf(rel, HASH_METAPAGE, HASH_READ, LH_META_PAGE);
     628           4 :     metap = HashPageGetMeta(BufferGetPage(metabuf));
     629           4 :     stats.version = metap->hashm_version;
     630           4 :     stats.space_per_page = metap->hashm_bsize;
     631           4 :     _hash_relbuf(rel, metabuf);
     632             : 
     633             :     /* Get the current relation length */
     634           4 :     nblocks = RelationGetNumberOfBlocks(rel);
     635             : 
     636             :     /* prepare access strategy for this index */
     637           4 :     bstrategy = GetAccessStrategy(BAS_BULKREAD);
     638             : 
     639             :     /* Start from blkno 1 as 0th block is metapage */
     640          32 :     for (blkno = 1; blkno < nblocks; blkno++)
     641             :     {
     642             :         Buffer      buf;
     643             :         Page        page;
     644             : 
     645          28 :         CHECK_FOR_INTERRUPTS();
     646             : 
     647          28 :         buf = ReadBufferExtended(rel, MAIN_FORKNUM, blkno, RBM_NORMAL,
     648             :                                  bstrategy);
     649          28 :         LockBuffer(buf, BUFFER_LOCK_SHARE);
     650          28 :         page = (Page) BufferGetPage(buf);
     651             : 
     652          28 :         if (PageIsNew(page))
     653           0 :             stats.unused_pages++;
     654          28 :         else if (PageGetSpecialSize(page) !=
     655             :                  MAXALIGN(sizeof(HashPageOpaqueData)))
     656           0 :             ereport(ERROR,
     657             :                     (errcode(ERRCODE_INDEX_CORRUPTED),
     658             :                      errmsg("index \"%s\" contains corrupted page at block %u",
     659             :                             RelationGetRelationName(rel),
     660             :                             BufferGetBlockNumber(buf))));
     661             :         else
     662             :         {
     663             :             HashPageOpaque opaque;
     664             :             int         pagetype;
     665             : 
     666          28 :             opaque = HashPageGetOpaque(page);
     667          28 :             pagetype = opaque->hasho_flag & LH_PAGE_TYPE;
     668             : 
     669          28 :             if (pagetype == LH_BUCKET_PAGE)
     670             :             {
     671          24 :                 stats.bucket_pages++;
     672          24 :                 GetHashPageStats(page, &stats);
     673             :             }
     674           4 :             else if (pagetype == LH_OVERFLOW_PAGE)
     675             :             {
     676           0 :                 stats.overflow_pages++;
     677           0 :                 GetHashPageStats(page, &stats);
     678             :             }
     679           4 :             else if (pagetype == LH_BITMAP_PAGE)
     680           4 :                 stats.bitmap_pages++;
     681           0 :             else if (pagetype == LH_UNUSED_PAGE)
     682           0 :                 stats.unused_pages++;
     683             :             else
     684           0 :                 ereport(ERROR,
     685             :                         (errcode(ERRCODE_INDEX_CORRUPTED),
     686             :                          errmsg("unexpected page type 0x%04X in HASH index \"%s\" block %u",
     687             :                                 opaque->hasho_flag, RelationGetRelationName(rel),
     688             :                                 BufferGetBlockNumber(buf))));
     689             :         }
     690          28 :         UnlockReleaseBuffer(buf);
     691             :     }
     692             : 
     693             :     /* Done accessing the index */
     694           4 :     index_close(rel, AccessShareLock);
     695             : 
     696             :     /* Count unused pages as free space. */
     697           4 :     stats.free_space += (uint64) stats.unused_pages * stats.space_per_page;
     698             : 
     699             :     /*
     700             :      * Total space available for tuples excludes the metapage and the bitmap
     701             :      * pages.
     702             :      */
     703           4 :     total_space = (uint64) (nblocks - (stats.bitmap_pages + 1)) *
     704           4 :         stats.space_per_page;
     705             : 
     706           4 :     if (total_space == 0)
     707           0 :         free_percent = 0.0;
     708             :     else
     709           4 :         free_percent = 100.0 * stats.free_space / total_space;
     710             : 
     711             :     /*
     712             :      * Build a tuple descriptor for our result type
     713             :      */
     714           4 :     if (get_call_result_type(fcinfo, NULL, &tupleDesc) != TYPEFUNC_COMPOSITE)
     715           0 :         elog(ERROR, "return type must be a row type");
     716             : 
     717           4 :     tupleDesc = BlessTupleDesc(tupleDesc);
     718             : 
     719             :     /*
     720             :      * Build and return the tuple
     721             :      */
     722           4 :     values[0] = Int32GetDatum(stats.version);
     723           4 :     values[1] = Int64GetDatum((int64) stats.bucket_pages);
     724           4 :     values[2] = Int64GetDatum((int64) stats.overflow_pages);
     725           4 :     values[3] = Int64GetDatum((int64) stats.bitmap_pages);
     726           4 :     values[4] = Int64GetDatum((int64) stats.unused_pages);
     727           4 :     values[5] = Int64GetDatum(stats.live_items);
     728           4 :     values[6] = Int64GetDatum(stats.dead_items);
     729           4 :     values[7] = Float8GetDatum(free_percent);
     730           4 :     tuple = heap_form_tuple(tupleDesc, values, nulls);
     731             : 
     732           4 :     PG_RETURN_DATUM(HeapTupleGetDatum(tuple));
     733             : }
     734             : 
     735             : /* -------------------------------------------------
     736             :  * GetHashPageStats()
     737             :  *
     738             :  * Collect statistics of single hash page
     739             :  * -------------------------------------------------
     740             :  */
     741             : static void
     742          24 : GetHashPageStats(Page page, HashIndexStat *stats)
     743             : {
     744          24 :     OffsetNumber maxoff = PageGetMaxOffsetNumber(page);
     745             :     int         off;
     746             : 
     747             :     /* count live and dead tuples, and free space */
     748          24 :     for (off = FirstOffsetNumber; off <= maxoff; off++)
     749             :     {
     750           0 :         ItemId      id = PageGetItemId(page, off);
     751             : 
     752           0 :         if (!ItemIdIsDead(id))
     753           0 :             stats->live_items++;
     754             :         else
     755           0 :             stats->dead_items++;
     756             :     }
     757          24 :     stats->free_space += PageGetExactFreeSpace(page);
     758          24 : }

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