#include "postgres.h"
#include "access/heapam.h"
#include "access/htup_details.h"
#include "access/relation.h"
#include "access/visibilitymap.h"
#include "catalog/pg_am_d.h"
#include "commands/vacuum.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "storage/bufmgr.h"
#include "storage/freespace.h"
#include "storage/procarray.h"

Include dependency graph for pgstatapprox.c:

Data Structures
struct	output_type

Macros
#define	NUM_OUTPUT_COLUMNS 10

Typedefs
typedef struct output_type	output_type

Functions
	PG_FUNCTION_INFO_V1 (pgstattuple_approx)

	PG_FUNCTION_INFO_V1 (pgstattuple_approx_v1_5)

Datum	pgstattuple_approx_internal (Oid relid, FunctionCallInfo fcinfo)

static void	statapprox_heap (Relation rel, output_type *stat)

Datum	pgstattuple_approx (PG_FUNCTION_ARGS)

Datum	pgstattuple_approx_v1_5 (PG_FUNCTION_ARGS)

Macro Definition Documentation

◆ NUM_OUTPUT_COLUMNS

#define NUM_OUTPUT_COLUMNS 10

Definition at line 46 of file pgstatapprox.c.

Typedef Documentation

◆ output_type

typedef struct output_type output_type

Function Documentation

◆ PG_FUNCTION_INFO_V1() [1/2]

PG_FUNCTION_INFO_V1 ( pgstattuple_approx )

◆ PG_FUNCTION_INFO_V1() [2/2]

PG_FUNCTION_INFO_V1 ( pgstattuple_approx_v1_5 )

◆ pgstattuple_approx()

Datum pgstattuple_approx ( PG_FUNCTION_ARGS )

Definition at line 214 of file pgstatapprox.c.

 {
     Oid         relid = PG_GETARG_OID(0);
  
     if (!superuser())
         ereport(ERROR,
                 (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                  errmsg("must be superuser to use pgstattuple functions")));
  
     PG_RETURN_DATUM(pgstattuple_approx_internal(relid, fcinfo));
 }

References ereport, errcode(), errmsg(), ERROR, PG_GETARG_OID, PG_RETURN_DATUM, pgstattuple_approx_internal(), and superuser().

◆ pgstattuple_approx_internal()

Datum pgstattuple_approx_internal	(	Oid	relid,
		FunctionCallInfo	fcinfo
	)

Definition at line 242 of file pgstatapprox.c.

 {
     Relation    rel;
     output_type stat = {0};
     TupleDesc   tupdesc;
     bool        nulls[NUM_OUTPUT_COLUMNS];
     Datum       values[NUM_OUTPUT_COLUMNS];
     HeapTuple   ret;
     int         i = 0;
  
     if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
         elog(ERROR, "return type must be a row type");
  
     if (tupdesc->natts != NUM_OUTPUT_COLUMNS)
         elog(ERROR, "incorrect number of output arguments");
  
     rel = relation_open(relid, AccessShareLock);
  
     /*
      * Reject attempts to read non-local temporary relations; we would be
      * likely to get wrong data since we have no visibility into the owning
      * session's local buffers.
      */
     if (RELATION_IS_OTHER_TEMP(rel))
         ereport(ERROR,
                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                  errmsg("cannot access temporary tables of other sessions")));
  
     /*
      * We support only relation kinds with a visibility map and a free space
      * map.
      */
     if (!(rel->rd_rel->relkind == RELKIND_RELATION ||
           rel->rd_rel->relkind == RELKIND_MATVIEW ||
           rel->rd_rel->relkind == RELKIND_TOASTVALUE))
         ereport(ERROR,
                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                  errmsg("relation \"%s\" is of wrong relation kind",
                         RelationGetRelationName(rel)),
                  errdetail_relkind_not_supported(rel->rd_rel->relkind)));
  
     if (rel->rd_rel->relam != HEAP_TABLE_AM_OID)
         ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("only heap AM is supported")));
  
     statapprox_heap(rel, &stat);
  
     relation_close(rel, AccessShareLock);
  
     memset(nulls, 0, sizeof(nulls));
  
     values[i++] = Int64GetDatum(stat.table_len);
     values[i++] = Float8GetDatum(stat.scanned_percent);
     values[i++] = Int64GetDatum(stat.tuple_count);
     values[i++] = Int64GetDatum(stat.tuple_len);
     values[i++] = Float8GetDatum(stat.tuple_percent);
     values[i++] = Int64GetDatum(stat.dead_tuple_count);
     values[i++] = Int64GetDatum(stat.dead_tuple_len);
     values[i++] = Float8GetDatum(stat.dead_tuple_percent);
     values[i++] = Int64GetDatum(stat.free_space);
     values[i++] = Float8GetDatum(stat.free_percent);
  
     ret = heap_form_tuple(tupdesc, values, nulls);
     return HeapTupleGetDatum(ret);
 }

References AccessShareLock, elog, ereport, errcode(), errdetail_relkind_not_supported(), errmsg(), ERROR, Float8GetDatum(), get_call_result_type(), heap_form_tuple(), HeapTupleGetDatum(), i, Int64GetDatum(), TupleDescData::natts, NUM_OUTPUT_COLUMNS, RelationData::rd_rel, relation_close(), RELATION_IS_OTHER_TEMP, relation_open(), RelationGetRelationName, statapprox_heap(), TYPEFUNC_COMPOSITE, and values.

Referenced by pgstattuple_approx(), and pgstattuple_approx_v1_5().

◆ pgstattuple_approx_v1_5()

Datum pgstattuple_approx_v1_5 ( PG_FUNCTION_ARGS )

Definition at line 234 of file pgstatapprox.c.

 {
     Oid         relid = PG_GETARG_OID(0);
  
     PG_RETURN_DATUM(pgstattuple_approx_internal(relid, fcinfo));
 }

References PG_GETARG_OID, PG_RETURN_DATUM, and pgstattuple_approx_internal().

◆ statapprox_heap()

static void statapprox_heap	(	Relation	rel,
		output_type *	stat
	)

static

Definition at line 59 of file pgstatapprox.c.

 {
     BlockNumber scanned,
                 nblocks,
                 blkno;
     Buffer      vmbuffer = InvalidBuffer;
     BufferAccessStrategy bstrategy;
     TransactionId OldestXmin;
  
     OldestXmin = GetOldestNonRemovableTransactionId(rel);
     bstrategy = GetAccessStrategy(BAS_BULKREAD);
  
     nblocks = RelationGetNumberOfBlocks(rel);
     scanned = 0;
  
     for (blkno = 0; blkno < nblocks; blkno++)
     {
         Buffer      buf;
         Page        page;
         OffsetNumber offnum,
                     maxoff;
         Size        freespace;
  
         CHECK_FOR_INTERRUPTS();
  
         /*
          * If the page has only visible tuples, then we can find out the free
          * space from the FSM and move on.
          */
         if (VM_ALL_VISIBLE(rel, blkno, &vmbuffer))
         {
             freespace = GetRecordedFreeSpace(rel, blkno);
             stat->tuple_len += BLCKSZ - freespace;
             stat->free_space += freespace;
             continue;
         }
  
         buf = ReadBufferExtended(rel, MAIN_FORKNUM, blkno,
                                  RBM_NORMAL, bstrategy);
  
         LockBuffer(buf, BUFFER_LOCK_SHARE);
  
         page = BufferGetPage(buf);
  
         stat->free_space += PageGetExactFreeSpace(page);
  
         /* We may count the page as scanned even if it's new/empty */
         scanned++;
  
         if (PageIsNew(page) || PageIsEmpty(page))
         {
             UnlockReleaseBuffer(buf);
             continue;
         }
  
         /*
          * Look at each tuple on the page and decide whether it's live or
          * dead, then count it and its size. Unlike lazy_scan_heap, we can
          * afford to ignore problems and special cases.
          */
         maxoff = PageGetMaxOffsetNumber(page);
  
         for (offnum = FirstOffsetNumber;
              offnum <= maxoff;
              offnum = OffsetNumberNext(offnum))
         {
             ItemId      itemid;
             HeapTupleData tuple;
  
             itemid = PageGetItemId(page, offnum);
  
             if (!ItemIdIsUsed(itemid) || ItemIdIsRedirected(itemid) ||
                 ItemIdIsDead(itemid))
             {
                 continue;
             }
  
             Assert(ItemIdIsNormal(itemid));
  
             ItemPointerSet(&(tuple.t_self), blkno, offnum);
  
             tuple.t_data = (HeapTupleHeader) PageGetItem(page, itemid);
             tuple.t_len = ItemIdGetLength(itemid);
             tuple.t_tableOid = RelationGetRelid(rel);
  
             /*
              * We follow VACUUM's lead in counting INSERT_IN_PROGRESS tuples
              * as "dead" while DELETE_IN_PROGRESS tuples are "live".  We don't
              * bother distinguishing tuples inserted/deleted by our own
              * transaction.
              */
             switch (HeapTupleSatisfiesVacuum(&tuple, OldestXmin, buf))
             {
                 case HEAPTUPLE_LIVE:
                 case HEAPTUPLE_DELETE_IN_PROGRESS:
                     stat->tuple_len += tuple.t_len;
                     stat->tuple_count++;
                     break;
                 case HEAPTUPLE_DEAD:
                 case HEAPTUPLE_RECENTLY_DEAD:
                 case HEAPTUPLE_INSERT_IN_PROGRESS:
                     stat->dead_tuple_len += tuple.t_len;
                     stat->dead_tuple_count++;
                     break;
                 default:
                     elog(ERROR, "unexpected HeapTupleSatisfiesVacuum result");
                     break;
             }
         }
  
         UnlockReleaseBuffer(buf);
     }
  
     stat->table_len = (uint64) nblocks * BLCKSZ;
  
     /*
      * We don't know how many tuples are in the pages we didn't scan, so
      * extrapolate the live-tuple count to the whole table in the same way
      * that VACUUM does.  (Like VACUUM, we're not taking a random sample, so
      * just extrapolating linearly seems unsafe.)  There should be no dead
      * tuples in all-visible pages, so no correction is needed for that, and
      * we already accounted for the space in those pages, too.
      */
     stat->tuple_count = vac_estimate_reltuples(rel, nblocks, scanned,
                                                stat->tuple_count);
  
     /* It's not clear if we could get -1 here, but be safe. */
     stat->tuple_count = Max(stat->tuple_count, 0);
  
     /*
      * Calculate percentages if the relation has one or more pages.
      */
     if (nblocks != 0)
     {
         stat->scanned_percent = 100.0 * scanned / nblocks;
         stat->tuple_percent = 100.0 * stat->tuple_len / stat->table_len;
         stat->dead_tuple_percent = 100.0 * stat->dead_tuple_len / stat->table_len;
         stat->free_percent = 100.0 * stat->free_space / stat->table_len;
     }
  
     if (BufferIsValid(vmbuffer))
     {
         ReleaseBuffer(vmbuffer);
         vmbuffer = InvalidBuffer;
     }
 }

References Assert, BAS_BULKREAD, buf, BUFFER_LOCK_SHARE, BufferGetPage(), BufferIsValid(), CHECK_FOR_INTERRUPTS, elog, ERROR, FirstOffsetNumber, GetAccessStrategy(), GetOldestNonRemovableTransactionId(), GetRecordedFreeSpace(), HEAPTUPLE_DEAD, HEAPTUPLE_DELETE_IN_PROGRESS, HEAPTUPLE_INSERT_IN_PROGRESS, HEAPTUPLE_LIVE, HEAPTUPLE_RECENTLY_DEAD, HeapTupleSatisfiesVacuum(), InvalidBuffer, ItemIdGetLength, ItemIdIsDead, ItemIdIsNormal, ItemIdIsRedirected, ItemIdIsUsed, ItemPointerSet(), LockBuffer(), MAIN_FORKNUM, Max, OffsetNumberNext, PageGetExactFreeSpace(), PageGetItem(), PageGetItemId(), PageGetMaxOffsetNumber(), PageIsEmpty(), PageIsNew(), RBM_NORMAL, ReadBufferExtended(), RelationGetNumberOfBlocks, RelationGetRelid, ReleaseBuffer(), HeapTupleData::t_data, HeapTupleData::t_len, HeapTupleData::t_self, HeapTupleData::t_tableOid, UnlockReleaseBuffer(), vac_estimate_reltuples(), and VM_ALL_VISIBLE.

Referenced by pgstattuple_approx_internal().

Data Structures

Macros

Typedefs

Functions