mirror of https://github.com/postgres/postgres
Store -1 in attdisbursion to signal 'no duplicates in column'.
Centralize att_disbursion readout logic.
This commit is contained in:
Tom Lane
parent
5af4b04f31
commit
14f84cd821
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@ -7,7 +7,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.117 1999/08/08 17:13:10 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.118 1999/08/09 03:16:47 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -2346,36 +2346,46 @@ vc_updstats(Oid relid, int num_pages, int num_tuples, bool hasindex, VRelStats *
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}
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else if (stats->null_cnt <= 1 && stats->best_cnt == 1)
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{
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/* looks like we have a unique-key attribute */
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double total = ((double) stats->nonnull_cnt) + ((double) stats->null_cnt);
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selratio = 1.0 / total;
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}
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else if (VacAttrStatsLtGtValid(stats) && stats->min_cnt + stats->max_cnt == stats->nonnull_cnt)
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{
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/* exact result when there are just 1 or 2 values... */
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double min_cnt_d = stats->min_cnt,
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max_cnt_d = stats->max_cnt,
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null_cnt_d = stats->null_cnt;
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double total = ((double) stats->nonnull_cnt) + null_cnt_d;
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selratio = (min_cnt_d * min_cnt_d + max_cnt_d * max_cnt_d + null_cnt_d * null_cnt_d) / (total * total);
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/* looks like we have a unique-key attribute ---
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* flag this with special -1.0 flag value.
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*
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* The correct disbursion is 1.0/numberOfRows, but since
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* the relation row count can get updated without
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* recomputing disbursion, we want to store a "symbolic"
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* value and figure 1.0/numberOfRows on the fly.
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*/
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selratio = -1;
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}
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else
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{
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double most = (double) (stats->best_cnt > stats->null_cnt ? stats->best_cnt : stats->null_cnt);
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double total = ((double) stats->nonnull_cnt) + ((double) stats->null_cnt);
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if (VacAttrStatsLtGtValid(stats) &&
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stats->min_cnt + stats->max_cnt == stats->nonnull_cnt)
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{
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/* exact result when there are just 1 or 2 values... */
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double min_cnt_d = stats->min_cnt,
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max_cnt_d = stats->max_cnt,
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null_cnt_d = stats->null_cnt;
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double total = ((double) stats->nonnull_cnt) + null_cnt_d;
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/*
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* we assume count of other values are 20% of best
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* count in table
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*/
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selratio = (most * most + 0.20 * most * (total - most)) / (total * total);
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selratio = (min_cnt_d * min_cnt_d + max_cnt_d * max_cnt_d + null_cnt_d * null_cnt_d) / (total * total);
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}
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else
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{
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double most = (double) (stats->best_cnt > stats->null_cnt ? stats->best_cnt : stats->null_cnt);
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double total = ((double) stats->nonnull_cnt) + ((double) stats->null_cnt);
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/*
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* we assume count of other values are 20% of best
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* count in table
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*/
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selratio = (most * most + 0.20 * most * (total - most)) / (total * total);
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}
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/* Make sure calculated values are in-range */
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if (selratio < 0.0)
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selratio = 0.0;
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else if (selratio > 1.0)
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selratio = 1.0;
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}
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if (selratio < 0.0)
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selratio = 0.0;
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else if (selratio > 1.0)
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selratio = 1.0;
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attp->attdisbursion = selratio;
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/*
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@ -7,7 +7,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.43 1999/08/06 04:00:15 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.44 1999/08/09 03:16:43 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -23,7 +23,7 @@
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#include "optimizer/pathnode.h"
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#include "optimizer/paths.h"
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#include "parser/parsetree.h"
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#include "utils/syscache.h"
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#include "utils/lsyscache.h"
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static Path *best_innerjoin(List *join_paths, List *outer_relid);
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static List *sort_inner_and_outer(RelOptInfo *joinrel, RelOptInfo *outerrel, RelOptInfo *innerrel,
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@ -586,7 +586,6 @@ hash_inner_and_outer(Query *root,
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/*
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* Estimate disbursion of the specified Var
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* Generate some kind of estimate, no matter what...
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*
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* We use a default of 0.1 if we can't figure out anything better.
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* This will typically discourage use of a hash rather strongly,
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@ -598,24 +597,11 @@ static Cost
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estimate_disbursion(Query *root, Var *var)
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{
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Oid relid;
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HeapTuple atp;
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double disbursion;
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if (! IsA(var, Var))
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return 0.1;
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relid = getrelid(var->varno, root->rtable);
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atp = SearchSysCacheTuple(ATTNUM,
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ObjectIdGetDatum(relid),
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Int16GetDatum(var->varattno),
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0, 0);
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if (! HeapTupleIsValid(atp))
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return 0.1;
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disbursion = ((Form_pg_attribute) GETSTRUCT(atp))->attdisbursion;
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if (disbursion > 0.0)
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return disbursion;
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return 0.1;
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return (Cost) get_attdisbursion(relid, var->varattno, 0.1);
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}
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@ -10,7 +10,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.37 1999/08/02 02:05:41 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.38 1999/08/09 03:16:45 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -52,7 +52,6 @@ static bool getattstatistics(Oid relid, AttrNumber attnum,
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Datum *commonval,
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Datum *loval,
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Datum *hival);
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static double getattdisbursion(Oid relid, AttrNumber attnum);
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/*
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@ -172,7 +171,7 @@ eqsel(Oid opid,
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/* No VACUUM ANALYZE stats available, so make a guess using
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* the disbursion stat (if we have that, which is unlikely...)
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*/
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selec = getattdisbursion(relid, attno);
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selec = get_attdisbursion(relid, attno, 0.01);
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}
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*result = (float64data) selec;
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@ -374,8 +373,8 @@ eqjoinsel(Oid opid,
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*result = 0.1;
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else
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{
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num1 = getattdisbursion(relid1, attno1);
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num2 = getattdisbursion(relid2, attno2);
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num1 = get_attdisbursion(relid1, attno1, 0.01);
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num2 = get_attdisbursion(relid2, attno2, 0.01);
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max = (num1 > num2) ? num1 : num2;
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if (max <= 0)
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*result = 1.0;
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@ -675,60 +674,6 @@ getattstatistics(Oid relid, AttrNumber attnum, Oid typid, int32 typmod,
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return true;
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}
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/*
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* getattdisbursion
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* Retrieve the disbursion statistic for an attribute,
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* or produce an estimate if no info is available.
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*/
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static double
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getattdisbursion(Oid relid, AttrNumber attnum)
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{
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HeapTuple atp;
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double disbursion;
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int32 ntuples;
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atp = SearchSysCacheTuple(ATTNUM,
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ObjectIdGetDatum(relid),
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Int16GetDatum(attnum),
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0, 0);
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if (!HeapTupleIsValid(atp))
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{
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/* this should not happen */
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elog(ERROR, "getattdisbursion: no attribute tuple %u %d",
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relid, attnum);
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return 0.1;
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}
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disbursion = ((Form_pg_attribute) GETSTRUCT(atp))->attdisbursion;
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if (disbursion > 0.0)
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return disbursion;
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/* VACUUM ANALYZE has not stored a disbursion statistic for us.
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* Produce an estimate = 1/numtuples. This may produce
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* unreasonably small estimates for large tables, so limit
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* the estimate to no less than 0.01.
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*/
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atp = SearchSysCacheTuple(RELOID,
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ObjectIdGetDatum(relid),
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0, 0, 0);
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if (!HeapTupleIsValid(atp))
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{
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/* this should not happen */
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elog(ERROR, "getattdisbursion: no relation tuple %u", relid);
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return 0.1;
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}
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ntuples = ((Form_pg_class) GETSTRUCT(atp))->reltuples;
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if (ntuples > 0)
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disbursion = 1.0 / (double) ntuples;
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if (disbursion < 0.01)
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disbursion = 0.01;
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return disbursion;
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}
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float64
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btreesel(Oid operatorObjectId,
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Oid indrelid,
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