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costing us lots more to maintain than it was worth. On shared tables it was of exactly zero benefit because we couldn't trust it to be up to date. On temp tables it sometimes saved an lseek, but not often enough to be worth getting excited about. And the real problem was that we forced an lseek on every relcache flush in order to update the field. So all in all it seems best to lose the complexity.
223 lines
5.7 KiB
C
223 lines
5.7 KiB
C
/*
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* $PostgreSQL: pgsql/contrib/pgstattuple/pgstattuple.c,v 1.15 2004/05/08 19:09:24 tgl Exp $
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*
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* Copyright (c) 2001,2002 Tatsuo Ishii
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*
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* Permission to use, copy, modify, and distribute this software and
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* its documentation for any purpose, without fee, and without a
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* written agreement is hereby granted, provided that the above
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* copyright notice and this paragraph and the following two
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* paragraphs appear in all copies.
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*
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE TO ANY PARTY FOR DIRECT,
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* INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
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* LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
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* DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* THE AUTHOR SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS
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* IS" BASIS, AND THE AUTHOR HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE,
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* SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
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*/
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#include "postgres.h"
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#include "fmgr.h"
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#include "funcapi.h"
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#include "access/heapam.h"
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#include "access/transam.h"
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#include "catalog/namespace.h"
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#include "utils/builtins.h"
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PG_FUNCTION_INFO_V1(pgstattuple);
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PG_FUNCTION_INFO_V1(pgstattuplebyid);
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extern Datum pgstattuple(PG_FUNCTION_ARGS);
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extern Datum pgstattuplebyid(PG_FUNCTION_ARGS);
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static Datum pgstattuple_real(Relation rel);
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/* ----------
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* pgstattuple:
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* returns live/dead tuples info
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*
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* C FUNCTION definition
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* pgstattuple(text) returns pgstattuple_type
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* see pgstattuple.sql for pgstattuple_type
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* ----------
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*/
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#define DUMMY_TUPLE "public.pgstattuple_type"
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#define NCOLUMNS 9
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#define NCHARS 32
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Datum
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pgstattuple(PG_FUNCTION_ARGS)
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{
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text *relname = PG_GETARG_TEXT_P(0);
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RangeVar *relrv;
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Relation rel;
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Datum result;
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/* open relation */
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relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname,
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"pgstattuple"));
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rel = heap_openrv(relrv, AccessShareLock);
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result = pgstattuple_real(rel);
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PG_RETURN_DATUM(result);
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}
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Datum
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pgstattuplebyid(PG_FUNCTION_ARGS)
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{
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Oid relid = PG_GETARG_OID(0);
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Relation rel;
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Datum result;
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/* open relation */
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rel = heap_open(relid, AccessShareLock);
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result = pgstattuple_real(rel);
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PG_RETURN_DATUM(result);
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}
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/*
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* pgstattuple_real
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*
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* The real work occurs here
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*/
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static Datum
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pgstattuple_real(Relation rel)
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{
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HeapScanDesc scan;
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HeapTuple tuple;
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BlockNumber nblocks;
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BlockNumber block = 0; /* next block to count free space in */
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BlockNumber tupblock;
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Buffer buffer;
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uint64 table_len;
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uint64 tuple_len = 0;
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uint64 dead_tuple_len = 0;
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uint64 tuple_count = 0;
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uint64 dead_tuple_count = 0;
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double tuple_percent;
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double dead_tuple_percent;
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uint64 free_space = 0; /* free/reusable space in bytes */
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double free_percent; /* free/reusable space in % */
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TupleDesc tupdesc;
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AttInMetadata *attinmeta;
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char **values;
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int i;
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Datum result;
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/*
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* Build a tuple description for a pgstattupe_type tuple
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*/
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tupdesc = RelationNameGetTupleDesc(DUMMY_TUPLE);
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/*
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* Generate attribute metadata needed later to produce tuples from raw
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* C strings
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*/
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attinmeta = TupleDescGetAttInMetadata(tupdesc);
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scan = heap_beginscan(rel, SnapshotAny, 0, NULL);
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nblocks = scan->rs_nblocks; /* # blocks to be scanned */
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/* scan the relation */
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while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
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{
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if (HeapTupleSatisfiesNow(tuple->t_data))
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{
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tuple_len += tuple->t_len;
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tuple_count++;
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}
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else
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{
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dead_tuple_len += tuple->t_len;
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dead_tuple_count++;
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}
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/*
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* To avoid physically reading the table twice, try to do the
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* free-space scan in parallel with the heap scan. However,
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* heap_getnext may find no tuples on a given page, so we cannot
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* simply examine the pages returned by the heap scan.
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*/
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tupblock = BlockIdGetBlockNumber(&tuple->t_self.ip_blkid);
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while (block <= tupblock)
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{
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buffer = ReadBuffer(rel, block);
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free_space += PageGetFreeSpace((Page) BufferGetPage(buffer));
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ReleaseBuffer(buffer);
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block++;
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}
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}
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heap_endscan(scan);
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while (block < nblocks)
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{
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buffer = ReadBuffer(rel, block);
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free_space += PageGetFreeSpace((Page) BufferGetPage(buffer));
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ReleaseBuffer(buffer);
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block++;
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}
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heap_close(rel, AccessShareLock);
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table_len = (uint64) nblocks *BLCKSZ;
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if (nblocks == 0)
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{
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tuple_percent = 0.0;
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dead_tuple_percent = 0.0;
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free_percent = 0.0;
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}
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else
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{
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tuple_percent = (double) tuple_len *100.0 / table_len;
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dead_tuple_percent = (double) dead_tuple_len *100.0 / table_len;
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free_percent = (double) free_space *100.0 / table_len;
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}
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/*
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* Prepare a values array for constructing the tuple. This should be an
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* array of C strings which will be processed later by the appropriate
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* "in" functions.
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*/
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values = (char **) palloc(NCOLUMNS * sizeof(char *));
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for (i = 0; i < NCOLUMNS; i++)
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values[i] = (char *) palloc(NCHARS * sizeof(char));
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i = 0;
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snprintf(values[i++], NCHARS, INT64_FORMAT, table_len);
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snprintf(values[i++], NCHARS, INT64_FORMAT, tuple_count);
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snprintf(values[i++], NCHARS, INT64_FORMAT, tuple_len);
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snprintf(values[i++], NCHARS, "%.2f", tuple_percent);
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snprintf(values[i++], NCHARS, INT64_FORMAT, dead_tuple_count);
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snprintf(values[i++], NCHARS, INT64_FORMAT, dead_tuple_len);
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snprintf(values[i++], NCHARS, "%.2f", dead_tuple_percent);
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snprintf(values[i++], NCHARS, INT64_FORMAT, free_space);
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snprintf(values[i++], NCHARS, "%.2f", free_percent);
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/* build a tuple */
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tuple = BuildTupleFromCStrings(attinmeta, values);
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/* make the tuple into a datum */
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result = HeapTupleGetDatum(tuple);
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/* Clean up */
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for (i = 0; i < NCOLUMNS; i++)
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pfree(values[i]);
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pfree(values);
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return (result);
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}
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