was rejecting negative attnums as bogus, which of course they are not.
Add code to get_attdisbursion to produce a useful value for OID attribute,
since VACUUM does not store stats for system attributes.
Also, repair bug that's been in eqjoinsel for a long time: it was taking
the max of the two columns' disbursions, whereas it should use the min.
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/optimizer/path/clausesel.c,v 1.25 1999/07/25 23:07:24 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/optimizer/path/clausesel.c,v 1.26 1999/09/09 02:35:47 tgl Exp $
*
*-------------------------------------------------------------------------
*/
int flag;
get_relattval(clause, 0, &relidx, &attno, &constval, &flag);
- if (relidx <= 0 || attno <= 0)
+ if (relidx && attno)
+ s1 = (Cost) restriction_selectivity(oprrest,
+ opno,
+ getrelid(relidx,
+ root->rtable),
+ attno,
+ constval,
+ flag);
+ else
{
/*
- * attno can be Invalid if the clause had a function in it,
+ * attno can be 0 if the clause had a function in it,
* i.e. WHERE myFunc(f) = 10
*
* XXX should be FIXED to use function selectivity
*/
s1 = (Cost) (0.5);
}
- else
- s1 = (Cost) restriction_selectivity(oprrest,
- opno,
- getrelid(relidx,
- root->rtable),
- attno,
- constval,
- flag);
}
}
else
attno2;
get_rels_atts(clause, &relid1, &attno1, &relid2, &attno2);
- if (relid1 > 0 && relid2 > 0 && attno1 > 0 && attno2 > 0)
+ if (relid1 && relid2 && attno1 && attno2)
+
s1 = (Cost) join_selectivity(oprjoin,
opno,
getrelid(relid1,
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.50 1999/08/26 05:09:05 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.51 1999/09/09 02:35:53 tgl Exp $
*
* HISTORY
* AUTHOR DATE MAJOR EVENT
*
* Returns the left operand of a clause of the form (op expr expr)
* or (op expr)
- * NB: it is assumed (for now) that all expr must be Var nodes
+ *
+ * NB: for historical reasons, the result is declared Var *, even
+ * though many callers can cope with results that are not Vars.
+ * The result really ought to be declared Expr * or Node *.
*/
Var *
get_leftop(Expr *clause)
* if the "something" is a constant, the value of the constant
* flags indicating whether a constant was found, and on which side.
* Default values are returned if the expression is too complicated,
- * specifically -1 for the relid and attno, 0 for the constant value.
- * Note that InvalidAttrNumber is *not* -1, but 0.
+ * specifically 0 for the relid and attno, 0 for the constant value.
+ *
+ * Note that negative attno values are *not* invalid, but represent
+ * system attributes such as OID. It's sufficient to check for relid=0
+ * to determine whether the routine succeeded.
*/
void
get_relattval(Node *clause,
{
/* Duh, it's too complicated for me... */
default_results:
- *relid = -1;
- *attno = -1;
+ *relid = 0;
+ *attno = 0;
*constval = 0;
*flag = 0;
return;
* for a joinclause.
*
* If the clause is not of the form (var op var) or if any of the vars
- * refer to nested attributes, then -1's are returned.
+ * refer to nested attributes, then zeroes are returned.
*
*/
void
AttrNumber *attno2)
{
/* set default values */
- *relid1 = -1;
- *attno1 = -1;
- *relid2 = -1;
- *attno2 = -1;
+ *relid1 = 0;
+ *attno1 = 0;
+ *relid2 = 0;
+ *attno2 = 0;
if (is_opclause(clause))
{
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/optimizer/util/plancat.c,v 1.36 1999/07/25 23:07:26 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/optimizer/util/plancat.c,v 1.37 1999/09/09 02:35:53 tgl Exp $
*
*-------------------------------------------------------------------------
*/
}
/*
- * restriction_selectivity in lisp system.
+ * restriction_selectivity
*
* NOTE: The routine is now merged with RestrictionClauseSelectivity
* as defined in plancat.c
* operator relation, by calling the function manager.
*
* XXX The assumption in the selectivity procedures is that if the
- * relation OIDs or attribute numbers are -1, then the clause
+ * relation OIDs or attribute numbers are 0, then the clause
* isn't of the form (op var const).
*/
Cost
* information.
*
* XXX The assumption in the selectivity procedures is that if the
- * relation OIDs or attribute numbers are -1, then the clause
+ * relation OIDs or attribute numbers are 0, then the clause
* isn't of the form (op var var).
*/
Cost
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.39 1999/08/21 00:56:18 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.40 1999/09/09 02:35:58 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "utils/syscache.h"
/* N is not a valid var/constant or relation id */
-#define NONVALUE(N) ((N) == -1)
+#define NONVALUE(N) ((N) == 0)
/* are we looking at a functional index selectivity request? */
#define FunctionalSelectivity(nIndKeys,attNum) ((attNum)==InvalidAttrNumber)
else
{
/* No VACUUM ANALYZE stats available, so make a guess using
- * the disbursion stat (if we have that, which is unlikely...)
+ * the disbursion stat (if we have that, which is unlikely
+ * for a normal attribute; but for a system attribute we may
+ * be able to estimate it).
*/
selec = get_attdisbursion(relid, attno, 0.01);
}
float64 result;
float64data num1,
num2,
- max;
+ min;
result = (float64) palloc(sizeof(float64data));
if (NONVALUE(attno1) || NONVALUE(relid1) ||
{
num1 = get_attdisbursion(relid1, attno1, 0.01);
num2 = get_attdisbursion(relid2, attno2, 0.01);
- max = (num1 > num2) ? num1 : num2;
- if (max <= 0)
- *result = 1.0;
- else
- *result = max;
+ /*
+ * The join selectivity cannot be more than num2, since each
+ * tuple in table 1 could match no more than num2 fraction of
+ * tuples in table 2 (and that's only if the table-1 tuple
+ * matches the most common value in table 2, so probably it's
+ * less). By the same reasoning it is not more than num1.
+ * The min is therefore an upper bound.
+ *
+ * XXX can we make a better estimate here? Using the nullfrac
+ * statistic might be helpful, for example. Assuming the operator
+ * is strict (does not succeed for null inputs) then the selectivity
+ * couldn't be more than (1-nullfrac1)*(1-nullfrac2), which might
+ * be usefully small if there are many nulls. How about applying
+ * the operator to the most common values?
+ */
+ min = (num1 < num2) ? num1 : num2;
+ *result = min;
}
return result;
}
* Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/utils/cache/lsyscache.c,v 1.33 1999/08/16 02:06:25 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/cache/lsyscache.c,v 1.34 1999/09/09 02:36:04 tgl Exp $
*
* NOTES
* Eventually, the index information should go through here, too.
if (disbursion < 0.0) /* VACUUM thinks there are no duplicates */
return 1.0 / (double) ntuples;
+ /*
+ * VACUUM ANALYZE does not compute disbursion for system attributes,
+ * but some of them can reasonably be assumed unique anyway.
+ */
+ if (attnum == ObjectIdAttributeNumber ||
+ attnum == SelfItemPointerAttributeNumber)
+ return 1.0 / (double) ntuples;
+
/*
* VACUUM ANALYZE has not been run for this table.
* Produce an estimate = 1/numtuples. This may produce
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