mirror of
https://github.com/postgres/postgres.git
synced 2025-07-02 09:02:37 +03:00
Rewrite of planner statistics-gathering code. ANALYZE is now available as
a separate statement (though it can still be invoked as part of VACUUM, too). pg_statistic redesigned to be more flexible about what statistics are stored. ANALYZE now collects a list of several of the most common values, not just one, plus a histogram (not just the min and max values). Random sampling is used to make the process reasonably fast even on very large tables. The number of values and histogram bins collected is now user-settable via an ALTER TABLE command. There is more still to do; the new stats are not being used everywhere they could be in the planner. But the remaining changes for this project should be localized, and the behavior is already better than before. A not-very-related change is that sorting now makes use of btree comparison routines if it can find one, rather than invoking '<' twice.
This commit is contained in:
Tom Lane
259
src/backend/utils/cache/lsyscache.c
vendored
259
src/backend/utils/cache/lsyscache.c
vendored
@ -7,7 +7,7 @@
|
||||
* Portions Copyright (c) 1994, Regents of the University of California
|
||||
*
|
||||
* IDENTIFICATION
|
||||
* $Header: /cvsroot/pgsql/src/backend/utils/cache/lsyscache.c,v 1.52 2001/03/23 04:49:55 momjian Exp $
|
||||
* $Header: /cvsroot/pgsql/src/backend/utils/cache/lsyscache.c,v 1.53 2001/05/07 00:43:24 tgl Exp $
|
||||
*
|
||||
* NOTES
|
||||
* Eventually, the index information should go through here, too.
|
||||
@ -18,7 +18,10 @@
|
||||
#include "access/tupmacs.h"
|
||||
#include "catalog/pg_operator.h"
|
||||
#include "catalog/pg_proc.h"
|
||||
#include "catalog/pg_statistic.h"
|
||||
#include "catalog/pg_type.h"
|
||||
#include "utils/array.h"
|
||||
#include "utils/builtins.h"
|
||||
#include "utils/lsyscache.h"
|
||||
#include "utils/syscache.h"
|
||||
|
||||
@ -182,106 +185,6 @@ get_atttypmod(Oid relid, AttrNumber attnum)
|
||||
return -1;
|
||||
}
|
||||
|
||||
/*
|
||||
* get_attdispersion
|
||||
*
|
||||
* Retrieve the dispersion statistic for an attribute,
|
||||
* or produce an estimate if no info is available.
|
||||
*
|
||||
* min_estimate is the minimum estimate to return if insufficient data
|
||||
* is available to produce a reliable value. This value may vary
|
||||
* depending on context. (For example, when deciding whether it is
|
||||
* safe to use a hashjoin, we want to be more conservative than when
|
||||
* estimating the number of tuples produced by an equijoin.)
|
||||
*/
|
||||
double
|
||||
get_attdispersion(Oid relid, AttrNumber attnum, double min_estimate)
|
||||
{
|
||||
HeapTuple atp;
|
||||
Form_pg_attribute att_tup;
|
||||
double dispersion;
|
||||
Oid atttypid;
|
||||
int32 ntuples;
|
||||
|
||||
atp = SearchSysCache(ATTNUM,
|
||||
ObjectIdGetDatum(relid),
|
||||
Int16GetDatum(attnum),
|
||||
0, 0);
|
||||
if (!HeapTupleIsValid(atp))
|
||||
{
|
||||
/* this should not happen */
|
||||
elog(ERROR, "get_attdispersion: no attribute tuple %u %d",
|
||||
relid, attnum);
|
||||
return min_estimate;
|
||||
}
|
||||
|
||||
att_tup = (Form_pg_attribute) GETSTRUCT(atp);
|
||||
|
||||
dispersion = att_tup->attdispersion;
|
||||
atttypid = att_tup->atttypid;
|
||||
|
||||
ReleaseSysCache(atp);
|
||||
|
||||
if (dispersion > 0.0)
|
||||
return dispersion; /* we have a specific estimate from VACUUM */
|
||||
|
||||
/*
|
||||
* Special-case boolean columns: the dispersion of a boolean is highly
|
||||
* unlikely to be anywhere near 1/numtuples, instead it's probably
|
||||
* more like 0.5.
|
||||
*
|
||||
* Are there any other cases we should wire in special estimates for?
|
||||
*/
|
||||
if (atttypid == BOOLOID)
|
||||
return 0.5;
|
||||
|
||||
/*
|
||||
* Dispersion is either 0 (no data available) or -1 (dispersion is
|
||||
* 1/numtuples). Either way, we need the relation size.
|
||||
*/
|
||||
|
||||
atp = SearchSysCache(RELOID,
|
||||
ObjectIdGetDatum(relid),
|
||||
0, 0, 0);
|
||||
if (!HeapTupleIsValid(atp))
|
||||
{
|
||||
/* this should not happen */
|
||||
elog(ERROR, "get_attdispersion: no relation tuple %u", relid);
|
||||
return min_estimate;
|
||||
}
|
||||
|
||||
ntuples = ((Form_pg_class) GETSTRUCT(atp))->reltuples;
|
||||
|
||||
ReleaseSysCache(atp);
|
||||
|
||||
if (ntuples == 0)
|
||||
return min_estimate; /* no data available */
|
||||
|
||||
if (dispersion < 0.0) /* VACUUM thinks there are no duplicates */
|
||||
return 1.0 / (double) ntuples;
|
||||
|
||||
/*
|
||||
* VACUUM ANALYZE does not compute dispersion for system attributes,
|
||||
* but some of them can reasonably be assumed unique anyway.
|
||||
*/
|
||||
if (attnum == ObjectIdAttributeNumber ||
|
||||
attnum == SelfItemPointerAttributeNumber)
|
||||
return 1.0 / (double) ntuples;
|
||||
if (attnum == TableOidAttributeNumber)
|
||||
return 1.0;
|
||||
|
||||
/*
|
||||
* VACUUM ANALYZE has not been run for this table. Produce an estimate
|
||||
* of 1/numtuples. This may produce unreasonably small estimates for
|
||||
* large tables, so limit the estimate to no less than min_estimate.
|
||||
*/
|
||||
dispersion = 1.0 / (double) ntuples;
|
||||
if (dispersion < min_estimate)
|
||||
dispersion = min_estimate;
|
||||
|
||||
return dispersion;
|
||||
}
|
||||
|
||||
/* ---------- INDEX CACHE ---------- */
|
||||
|
||||
/* watch this space...
|
||||
@ -876,3 +779,157 @@ get_typtype(Oid typid)
|
||||
}
|
||||
|
||||
#endif
|
||||
|
||||
/* ---------- STATISTICS CACHE ---------- */
|
||||
|
||||
/*
|
||||
* get_attstatsslot
|
||||
*
|
||||
* Extract the contents of a "slot" of a pg_statistic tuple.
|
||||
* Returns TRUE if requested slot type was found, else FALSE.
|
||||
*
|
||||
* Unlike other routines in this file, this takes a pointer to an
|
||||
* already-looked-up tuple in the pg_statistic cache. We do this since
|
||||
* most callers will want to extract more than one value from the cache
|
||||
* entry, and we don't want to repeat the cache lookup unnecessarily.
|
||||
*
|
||||
* statstuple: pg_statistics tuple to be examined.
|
||||
* atttype: type OID of attribute.
|
||||
* atttypmod: typmod of attribute.
|
||||
* reqkind: STAKIND code for desired statistics slot kind.
|
||||
* reqop: STAOP value wanted, or InvalidOid if don't care.
|
||||
* values, nvalues: if not NULL, the slot's stavalues are extracted.
|
||||
* numbers, nnumbers: if not NULL, the slot's stanumbers are extracted.
|
||||
*
|
||||
* If assigned, values and numbers are set to point to palloc'd arrays.
|
||||
* If the attribute type is pass-by-reference, the values referenced by
|
||||
* the values array are themselves palloc'd. The palloc'd stuff can be
|
||||
* freed by calling free_attstatsslot.
|
||||
*/
|
||||
bool
|
||||
get_attstatsslot(HeapTuple statstuple,
|
||||
Oid atttype, int32 atttypmod,
|
||||
int reqkind, Oid reqop,
|
||||
Datum **values, int *nvalues,
|
||||
float4 **numbers, int *nnumbers)
|
||||
{
|
||||
Form_pg_statistic stats = (Form_pg_statistic) GETSTRUCT(statstuple);
|
||||
int i,
|
||||
j;
|
||||
Datum val;
|
||||
bool isnull;
|
||||
ArrayType *statarray;
|
||||
int narrayelem;
|
||||
HeapTuple typeTuple;
|
||||
FmgrInfo inputproc;
|
||||
Oid typelem;
|
||||
|
||||
for (i = 0; i < STATISTIC_NUM_SLOTS; i++)
|
||||
{
|
||||
if ((&stats->stakind1)[i] == reqkind &&
|
||||
(reqop == InvalidOid || (&stats->staop1)[i] == reqop))
|
||||
break;
|
||||
}
|
||||
if (i >= STATISTIC_NUM_SLOTS)
|
||||
return false; /* not there */
|
||||
|
||||
if (values)
|
||||
{
|
||||
val = SysCacheGetAttr(STATRELATT, statstuple,
|
||||
Anum_pg_statistic_stavalues1 + i,
|
||||
&isnull);
|
||||
if (isnull)
|
||||
elog(ERROR, "get_attstatsslot: stavalues is null");
|
||||
statarray = DatumGetArrayTypeP(val);
|
||||
/*
|
||||
* Do initial examination of the array. This produces a list
|
||||
* of text Datums --- ie, pointers into the text array value.
|
||||
*/
|
||||
deconstruct_array(statarray, false, -1, 'i', values, nvalues);
|
||||
narrayelem = *nvalues;
|
||||
/*
|
||||
* We now need to replace each text Datum by its internal equivalent.
|
||||
*
|
||||
* Get the type input proc and typelem for the column datatype.
|
||||
*/
|
||||
typeTuple = SearchSysCache(TYPEOID,
|
||||
ObjectIdGetDatum(atttype),
|
||||
0, 0, 0);
|
||||
if (!HeapTupleIsValid(typeTuple))
|
||||
elog(ERROR, "get_attstatsslot: Cache lookup failed for type %u",
|
||||
atttype);
|
||||
fmgr_info(((Form_pg_type) GETSTRUCT(typeTuple))->typinput, &inputproc);
|
||||
typelem = ((Form_pg_type) GETSTRUCT(typeTuple))->typelem;
|
||||
ReleaseSysCache(typeTuple);
|
||||
/*
|
||||
* Do the conversions. The palloc'd array of Datums is reused
|
||||
* in place.
|
||||
*/
|
||||
for (j = 0; j < narrayelem; j++)
|
||||
{
|
||||
char *strval;
|
||||
|
||||
strval = DatumGetCString(DirectFunctionCall1(textout,
|
||||
(*values)[j]));
|
||||
(*values)[j] = FunctionCall3(&inputproc,
|
||||
CStringGetDatum(strval),
|
||||
ObjectIdGetDatum(typelem),
|
||||
Int32GetDatum(atttypmod));
|
||||
pfree(strval);
|
||||
}
|
||||
/*
|
||||
* Free statarray if it's a detoasted copy.
|
||||
*/
|
||||
if ((Pointer) statarray != DatumGetPointer(val))
|
||||
pfree(statarray);
|
||||
}
|
||||
|
||||
if (numbers)
|
||||
{
|
||||
val = SysCacheGetAttr(STATRELATT, statstuple,
|
||||
Anum_pg_statistic_stanumbers1 + i,
|
||||
&isnull);
|
||||
if (isnull)
|
||||
elog(ERROR, "get_attstatsslot: stanumbers is null");
|
||||
statarray = DatumGetArrayTypeP(val);
|
||||
/*
|
||||
* We expect the array to be a 1-D float4 array; verify that.
|
||||
* We don't need to use deconstruct_array() since the array
|
||||
* data is just going to look like a C array of float4 values.
|
||||
*/
|
||||
narrayelem = ARR_DIMS(statarray)[0];
|
||||
if (ARR_NDIM(statarray) != 1 || narrayelem <= 0 ||
|
||||
ARR_SIZE(statarray) != (ARR_OVERHEAD(1) + narrayelem * sizeof(float4)))
|
||||
elog(ERROR, "get_attstatsslot: stanumbers is bogus");
|
||||
*numbers = (float4 *) palloc(narrayelem * sizeof(float4));
|
||||
memcpy(*numbers, ARR_DATA_PTR(statarray), narrayelem * sizeof(float4));
|
||||
*nnumbers = narrayelem;
|
||||
/*
|
||||
* Free statarray if it's a detoasted copy.
|
||||
*/
|
||||
if ((Pointer) statarray != DatumGetPointer(val))
|
||||
pfree(statarray);
|
||||
}
|
||||
|
||||
return true;
|
||||
}
|
||||
|
||||
void
|
||||
free_attstatsslot(Oid atttype,
|
||||
Datum *values, int nvalues,
|
||||
float4 *numbers, int nnumbers)
|
||||
{
|
||||
if (values)
|
||||
{
|
||||
if (! get_typbyval(atttype))
|
||||
{
|
||||
int i;
|
||||
|
||||
for (i = 0; i < nvalues; i++)
|
||||
pfree(DatumGetPointer(values[i]));
|
||||
}
|
||||
pfree(values);
|
||||
}
|
||||
if (numbers)
|
||||
pfree(numbers);
|
||||
}
|
||||
|
||||
4
src/backend/utils/cache/syscache.c
vendored
4
src/backend/utils/cache/syscache.c
vendored
@ -8,7 +8,7 @@
|
||||
*
|
||||
*
|
||||
* IDENTIFICATION
|
||||
* $Header: /cvsroot/pgsql/src/backend/utils/cache/syscache.c,v 1.60 2001/03/22 03:59:57 momjian Exp $
|
||||
* $Header: /cvsroot/pgsql/src/backend/utils/cache/syscache.c,v 1.61 2001/05/07 00:43:24 tgl Exp $
|
||||
*
|
||||
* NOTES
|
||||
* These routines allow the parser/planner/executor to perform
|
||||
@ -313,7 +313,7 @@ static struct cachedesc cacheinfo[] = {
|
||||
0,
|
||||
0
|
||||
}},
|
||||
{StatisticRelationName, /* STATRELID */
|
||||
{StatisticRelationName, /* STATRELATT */
|
||||
StatisticRelidAttnumIndex,
|
||||
2,
|
||||
{
|
||||
|
||||
Reference in New Issue
Block a user