database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-06-16 06:01:02 +03:00
Code Activity

First cut at making useful selectivity estimates for range queries

Browse Source 
(ie, WHERE x > lowbound AND x < highbound).  It's not very bright yet
but it does something useful.  Also, rename intltsel/intgtsel to
scalarltsel/scalargtsel to reflect usage better.  Extend convert_to_scalar
to do something a little bit useful with string data types.  Still need
to make it do something with date/time datatypes, but I'll wait for
Thomas's datetime unification dust to settle first.  Eventually the
routine ought not have any type-specific knowledge at all; it ought to
be calling a type-dependent routine found via a pg_type column; but
that's a task for another day.
This commit is contained in:
Tom Lane
2000-01-24 07:16:52 +00:00
parent 8bcac56086
commit 0dbffa704a
9 changed files with 529 additions and 248 deletions
Download Patch File Download Diff File Expand all files Collapse all files

176
src/backend/utils/adt/selfuncs.c
View File

@ -14,7 +14,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.52 2000/01/24 02:12:55 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.53 2000/01/24 07:16:46 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -47,15 +47,13 @@
/* default selectivity estimate for inequalities such as "A < b" */
#define DEFAULT_INEQ_SEL (1.0 / 3.0)
static bool convert_to_scale(Datum value, Oid typid,
double *scaleval);
static void getattproperties(Oid relid, AttrNumber attnum,
Oid *typid,
int *typlen,
bool *typbyval,
int32 *typmod);
static bool getattstatistics(Oid relid, AttrNumber attnum,
Oid opid, Oid typid, int32 typmod,
Oid typid, int32 typmod,
double *nullfrac,
double *commonfrac,
Datum *commonval,
@ -100,7 +98,7 @@ eqsel(Oid opid,
&typid, &typlen, &typbyval, &typmod);
/* get stats for the attribute, if available */
if (getattstatistics(relid, attno, opid, typid, typmod,
if (getattstatistics(relid, attno, typid, typmod,
&nullfrac, &commonfrac, &commonval,
NULL, NULL))
{
@ -212,19 +210,18 @@ neqsel(Oid opid,
}
/*
* intltsel - Selectivity of "<" (also "<=") for integers.
* scalarltsel - Selectivity of "<" (also "<=") for scalars.
*
* Actually, this works and is used for all numeric types, so it should
* be renamed. In fact, it is also currently called for all manner of
* non-numeric types, for which it is NOT very helpful. That needs
* to be fixed.
* This routine works for any datatype (or pair of datatypes) known to
* convert_to_scalar(). If it is applied to some other datatype,
* it will return a default estimate.
*/
float64
intltsel(Oid opid,
Oid relid,
AttrNumber attno,
Datum value,
int32 flag)
scalarltsel(Oid opid,
Oid relid,
AttrNumber attno,
Datum value,
int32 flag)
{
float64 result;
@ -253,19 +250,19 @@ intltsel(Oid opid,
*/
oprtuple = get_operator_tuple(opid);
if (! HeapTupleIsValid(oprtuple))
elog(ERROR, "intltsel: no tuple for operator %u", opid);
elog(ERROR, "scalarltsel: no tuple for operator %u", opid);
ltype = ((Form_pg_operator) GETSTRUCT(oprtuple))->oprleft;
rtype = ((Form_pg_operator) GETSTRUCT(oprtuple))->oprright;
/* Convert the constant to a uniform comparison scale. */
if (! convert_to_scale(value,
((flag & SEL_RIGHT) ? rtype : ltype),
&val))
if (! convert_to_scalar(value,
((flag & SEL_RIGHT) ? rtype : ltype),
&val))
{
/* Ideally we'd produce an error here, on the grounds that
* the given operator shouldn't have intltsel registered as its
/* Ideally we'd produce an error here, on the grounds that the
* given operator shouldn't have scalarltsel registered as its
* selectivity func unless we can deal with its operand types.
* But currently, all manner of stuff is invoking intltsel,
* But currently, all manner of stuff is invoking scalarltsel,
* so give a default estimate until that can be fixed.
*/
*result = DEFAULT_INEQ_SEL;
@ -276,7 +273,7 @@ intltsel(Oid opid,
getattproperties(relid, attno,
&typid, &typlen, &typbyval, &typmod);
if (! getattstatistics(relid, attno, opid, typid, typmod,
if (! getattstatistics(relid, attno, typid, typmod,
NULL, NULL, NULL,
&loval, &hival))
{
@ -286,8 +283,8 @@ intltsel(Oid opid,
}
/* Convert the attribute's loval/hival to common scale. */
if (! convert_to_scale(loval, typid, &low) ||
! convert_to_scale(hival, typid, &high))
if (! convert_to_scalar(loval, typid, &low) ||
! convert_to_scalar(hival, typid, &high))
{
/* See above comments... */
if (! typbyval)
@ -341,23 +338,23 @@ intltsel(Oid opid,
}
/*
* intgtsel - Selectivity of ">" (also ">=") for integers.
* scalargtsel - Selectivity of ">" (also ">=") for integers.
*
* See above comments for intltsel.
* See above comments for scalarltsel.
*/
float64
intgtsel(Oid opid,
Oid relid,
AttrNumber attno,
Datum value,
int32 flag)
scalargtsel(Oid opid,
Oid relid,
AttrNumber attno,
Datum value,
int32 flag)
{
float64 result;
/* Compute selectivity of "<", then invert --- but only if we
* were able to produce a non-default estimate.
*/
result = intltsel(opid, relid, attno, value, flag);
result = scalarltsel(opid, relid, attno, value, flag);
if (*result != DEFAULT_INEQ_SEL)
*result = 1.0 - *result;
return result;
@ -429,14 +426,14 @@ neqjoinsel(Oid opid,
}
/*
* intltjoinsel - Join selectivity of "<" and "<="
* scalarltjoinsel - Join selectivity of "<" and "<=" for scalars
*/
float64
intltjoinsel(Oid opid,
Oid relid1,
AttrNumber attno1,
Oid relid2,
AttrNumber attno2)
scalarltjoinsel(Oid opid,
Oid relid1,
AttrNumber attno1,
Oid relid2,
AttrNumber attno2)
{
float64 result;
@ -446,14 +443,14 @@ intltjoinsel(Oid opid,
}
/*
* intgtjoinsel - Join selectivity of ">" and ">="
* scalargtjoinsel - Join selectivity of ">" and ">=" for scalars
*/
float64
intgtjoinsel(Oid opid,
Oid relid1,
AttrNumber attno1,
Oid relid2,
AttrNumber attno2)
scalargtjoinsel(Oid opid,
Oid relid1,
AttrNumber attno1,
Oid relid2,
AttrNumber attno2)
{
float64 result;
@ -463,21 +460,25 @@ intgtjoinsel(Oid opid,
}
/*
* convert_to_scale
* Convert a given value of the indicated type to the comparison
* scale needed by intltsel(). Returns "true" if successful.
* convert_to_scalar
* Convert a non-NULL value of the indicated type to the comparison
* scale needed by scalarltsel()/scalargtsel().
* Returns "true" if successful.
*
* All numeric datatypes are simply converted to their equivalent
* "double" values.
* Future extension: convert string-like types to some suitable scale.
* "double" values. String datatypes are converted to a crude scale
* using their first character (only if it is in the ASCII range,
* to try to avoid problems with non-ASCII collating sequences).
*/
static bool
convert_to_scale(Datum value, Oid typid,
double *scaleval)
bool
convert_to_scalar(Datum value, Oid typid,
double *scaleval)
{
/* Fast-path conversions for some built-in types */
switch (typid)
{
/*
* Built-in numeric types
*/
case BOOLOID:
*scaleval = (double) DatumGetUInt8(value);
return true;
@ -504,18 +505,54 @@ convert_to_scale(Datum value, Oid typid,
/* we can treat OIDs as integers... */
*scaleval = (double) DatumGetObjectId(value);
return true;
case TEXTOID:
/*
* Eventually this should get handled by somehow scaling as a
* string value. For now, we need to call it out to avoid
* falling into the default case, because there is a float8(text)
* function declared in pg_proc that will do the wrong thing :-(
*/
/*
* Built-in string types
*/
case CHAROID:
{
char ch = DatumGetChar(value);
if (ch >= 0 && ch < 127)
{
*scaleval = (double) ch;
return true;
}
break;
}
case BPCHAROID:
case VARCHAROID:
case TEXTOID:
if (VARSIZE(DatumGetPointer(value)) > VARHDRSZ)
{
char ch = * (char *) VARDATA(DatumGetPointer(value));
if (ch >= 0 && ch < 127)
{
*scaleval = (double) ch;
return true;
}
}
break;
case NAMEOID:
{
NameData *nm = (NameData *) DatumGetPointer(value);
char ch = NameStr(*nm)[0];
if (ch >= 0 && ch < 127)
{
*scaleval = (double) ch;
return true;
}
break;
}
default:
{
/* See whether there is a registered type-conversion function,
/*
* See whether there is a registered type-conversion function,
* namely a procedure named "float8" with the right signature.
* If so, assume we can convert the value to the numeric scale.
*/
Oid oid_array[FUNC_MAX_ARGS];
HeapTuple ftup;
@ -589,7 +626,9 @@ getattproperties(Oid relid, AttrNumber attnum,
* after use if the data type is not by-value.)
*/
static bool
getattstatistics(Oid relid, AttrNumber attnum, Oid opid, Oid typid,
getattstatistics(Oid relid,
AttrNumber attnum,
Oid typid,
int32 typmod,
double *nullfrac,
double *commonfrac,
@ -603,8 +642,15 @@ getattstatistics(Oid relid, AttrNumber attnum, Oid opid, Oid typid,
Oid typelem;
bool isnull;
/* We assume that there will only be one entry in pg_statistic
* for the given rel/att. Someday, VACUUM might store more than one...
/*
* We assume that there will only be one entry in pg_statistic for
* the given rel/att, so we search WITHOUT considering the staop
* column. Someday, VACUUM might store more than one entry per rel/att,
* corresponding to more than one possible sort ordering defined for
* the column type. However, to make that work we will need to figure
* out which staop to search for --- it's not necessarily the one we
* have at hand! (For example, we might have a '>' operator rather than
* the '<' operator that will appear in staop.)
*/
tuple = SearchSysCacheTuple(STATRELID,
ObjectIdGetDatum(relid),