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Avoid repeated detoasting (and possible memory leaks) when processing

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a toasted datum in VACUUM ANALYZE.
This commit is contained in:
Tom Lane
2000-12-02 19:38:34 +00:00
parent 079c60abc0
commit 77698e11a9
2 changed files with 64 additions and 36 deletions
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60
src/backend/commands/analyze.c
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@ -8,19 +8,18 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/commands/analyze.c,v 1.9 2000/11/16 22:30:19 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/commands/analyze.c,v 1.10 2000/12/02 19:38:34 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <sys/types.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include "postgres.h"
#include "access/heapam.h"
#include "catalog/catname.h"
#include "catalog/indexing.h"
@ -159,7 +158,8 @@ analyze_rel(Oid relid, List *anal_cols2, int MESSAGE_LEVEL)
stats = &vacattrstats[i];
stats->attr = palloc(ATTRIBUTE_TUPLE_SIZE);
memmove(stats->attr, attr[((attnums) ? attnums[i] : i)], ATTRIBUTE_TUPLE_SIZE);
memcpy(stats->attr, attr[((attnums) ? attnums[i] : i)],
ATTRIBUTE_TUPLE_SIZE);
stats->best = stats->guess1 = stats->guess2 = 0;
stats->max = stats->min = 0;
stats->best_len = stats->guess1_len = stats->guess2_len = 0;
@ -220,6 +220,7 @@ analyze_rel(Oid relid, List *anal_cols2, int MESSAGE_LEVEL)
/* delete existing pg_statistic rows for relation */
del_stats(relid, ((attnums) ? attr_cnt : 0), attnums);
/* scan relation to gather statistics */
scan = heap_beginscan(onerel, false, SnapshotNow, 0, NULL);
while (HeapTupleIsValid(tuple = heap_getnext(scan, 0)))
@ -237,7 +238,7 @@ analyze_rel(Oid relid, List *anal_cols2, int MESSAGE_LEVEL)
}
/*
* attr_stats() -- compute column statistics used by the optimzer
* attr_stats() -- compute column statistics used by the planner
*
* We compute the column min, max, null and non-null counts.
* Plus we attempt to find the count of the value that occurs most
@ -266,6 +267,7 @@ attr_stats(Relation onerel, int attr_cnt, VacAttrStats *vacattrstats, HeapTuple
for (i = 0; i < attr_cnt; i++)
{
VacAttrStats *stats = &vacattrstats[i];
Datum origvalue;
Datum value;
bool isnull;
bool value_hit;
@ -278,16 +280,25 @@ attr_stats(Relation onerel, int attr_cnt, VacAttrStats *vacattrstats, HeapTuple
continue;
#endif /* _DROP_COLUMN_HACK__ */
value = heap_getattr(tuple,
stats->attr->attnum, tupDesc, &isnull);
origvalue = heap_getattr(tuple, stats->attr->attnum,
tupDesc, &isnull);
if (isnull)
{
stats->null_cnt++;
continue;
}
stats->nonnull_cnt++;
/*
* If the value is toasted, detoast it to avoid repeated detoastings
* and resultant memory leakage inside the comparison routines.
*/
if (!stats->attr->attbyval && stats->attr->attlen == -1)
value = PointerGetDatum(PG_DETOAST_DATUM(origvalue));
else
value = origvalue;
if (! stats->initialized)
{
bucketcpy(stats->attr, value, &stats->best, &stats->best_len);
@ -365,22 +376,26 @@ attr_stats(Relation onerel, int attr_cnt, VacAttrStats *vacattrstats, HeapTuple
stats->guess1_hits = 1;
stats->guess2_hits = 1;
}
/* Clean up detoasted copy, if any */
if (value != origvalue)
pfree(DatumGetPointer(value));
}
}
/*
* bucketcpy() -- copy a new value into one of the statistics buckets
*
*/
static void
bucketcpy(Form_pg_attribute attr, Datum value, Datum *bucket, int *bucket_len)
{
if (attr->attbyval && attr->attlen != -1)
if (attr->attbyval)
*bucket = value;
else
{
int len = (attr->attlen != -1 ? attr->attlen : VARSIZE(value));
/* Avoid unnecessary palloc() traffic... */
if (len > *bucket_len)
{
if (*bucket_len != 0)
@ -396,8 +411,27 @@ bucketcpy(Form_pg_attribute attr, Datum value, Datum *bucket, int *bucket_len)
/*
* update_attstats() -- update attribute statistics for one relation
*
* Updates of pg_attribute statistics are handled by over-write,
* for reasons described above. pg_statistic rows are added normally.
* Statistics are stored in several places: the pg_class row for the
* relation has stats about the whole relation, the pg_attribute rows
* for each attribute store "dispersion", and there is a pg_statistic
* row for each (non-system) attribute. (Dispersion probably ought to
* be moved to pg_statistic, but it's not worth doing unless there's
* another reason to have to change pg_attribute.) The pg_class values
* are updated by VACUUM, not here.
*
* We violate no-overwrite semantics here by storing new values for
* the dispersion column directly into the pg_attribute tuple that's
* already on the page. The reason for this is that if we updated
* these tuples in the usual way, vacuuming pg_attribute itself
* wouldn't work very well --- by the time we got done with a vacuum
* cycle, most of the tuples in pg_attribute would've been obsoleted.
* Updating pg_attribute's own statistics would be especially tricky.
* Of course, this only works for fixed-size never-null columns, but
* dispersion is.
*
* pg_statistic rows are just added normally. This means that
* pg_statistic will probably contain some deleted rows at the
* completion of a vacuum cycle, unless it happens to get vacuumed last.
*
* To keep things simple, we punt for pg_statistic, and don't try
* to compute or store rows for pg_statistic itself in pg_statistic.