Heikki Linnakangas wrote:
Jan Urbański wrote:
Another thing are cstring_to_text_with_len calls. I'm doing them so I
can use bttextcmp in bsearch(). I think I could come up with a
dedicated function to return text Datums and WordEntries (read:
non-NULL terminated strings with a given length).
Just keep them as cstrings and use strcmp. We're only keeping the array
sorted so that we can binary search it, so we don't need proper
locale-dependent collation. Note that we already assume that two strings
('text's) are equal if and only if their binary representations are
equal (texteq() uses strcmp).
OK, I got rid of cstring->text calls and memory contexts as I went
through it. The only tiny ugliness is that there's one function used for
qsort() and another for bsearch(), because I'm sorting an array of texts
(from pg_statistic) and I'm binary searching for a lexeme (non-NULL
terminated string with length).
My medicore gprof skills got me:
0.00 0.22 5/5 OidFunctionCall4 [37]
[38] 28.4 0.00 0.22 5 tssel [38]
0.00 0.17 5/5
get_restriction_variable [40]
0.03 0.01 5/10 pg_qsort [60]
0.00 0.00 5/5 get_attstatsslot [139]
Hopefully that says that the qsort() overhead is small compared to
munging through the planner Node.
Revised version of the patch attached.
Cheers,
Jan
--
Jan Urbanski
GPG key ID: E583D7D2
ouden estin
diff --git a/src/backend/tsearch/Makefile b/src/backend/tsearch/Makefile
index e20a4a2..ba728eb 100644
*** a/src/backend/tsearch/Makefile
--- b/src/backend/tsearch/Makefile
***************
*** 19,25 ****
OBJS = ts_locale.o ts_parse.o wparser.o wparser_def.o dict.o \
dict_simple.o dict_synonym.o dict_thesaurus.o \
dict_ispell.o regis.o spell.o \
! to_tsany.o ts_typanalyze.o ts_utils.o
include $(top_srcdir)/src/backend/common.mk
--- 19,25 ----
OBJS = ts_locale.o ts_parse.o wparser.o wparser_def.o dict.o \
dict_simple.o dict_synonym.o dict_thesaurus.o \
dict_ispell.o regis.o spell.o \
! to_tsany.o ts_typanalyze.o ts_selfuncs.o ts_utils.o
include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/tsearch/ts_selfuncs.c
b/src/backend/tsearch/ts_selfuncs.c
new file mode 100644
index 0000000..4deb507
*** /dev/null
--- b/src/backend/tsearch/ts_selfuncs.c
***************
*** 0,-1 ****
--- 1,334 ----
+ /*-------------------------------------------------------------------------
+ *
+ * ts_selfuncs.c
+ * Selectivity functions for text search types.
+ *
+ * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ * $PostgreSQL$
+ *
+ *-------------------------------------------------------------------------
+ */
+ #include "postgres.h"
+
+ #include "miscadmin.h" /* for check_stack_depth() */
+ #include "utils/memutils.h"
+ #include "utils/builtins.h"
+ #include "utils/syscache.h"
+ #include "utils/lsyscache.h"
+ #include "utils/selfuncs.h"
+ #include "catalog/pg_type.h"
+ #include "catalog/pg_statistic.h"
+ #include "nodes/nodes.h"
+ #include "tsearch/ts_type.h"
+
+ /* lookup table type for binary searching through MCELEMs */
+ typedef struct
+ {
+ Datum element;
+ float4 frequency;
+ } TextFreq;
+
+ /* type of keys for bsearch()ing through an array of TextFreqs */
+ typedef struct
+ {
+ char *lexeme;
+ int length;
+ } LexemeKey;
+
+ static int
+ compare_two_textfreqs(const void *e1, const void *e2);
+ static int
+ compare_lexeme_textfreq(const void *e1, const void *e2);
+
+ static Selectivity
+ tsquery_opr_selec(QueryItem *item, char *operand, TextFreq *lookup,
+ int length, float4 minfreq);
+ static Selectivity
+ mcelem_tsquery_selec(TSQuery query, Datum *mcelem, int nmcelem,
+ float4 *numbers, int
nnumbers);
+ static double
+ tsquerysel(VariableStatData *vardata, Datum constval);
+
+
+ /* TSQuery traversal function */
+ static Selectivity
+ tsquery_opr_selec(QueryItem *item, char *operand, TextFreq *lookup,
+ int length, float4 minfreq)
+ {
+ LexemeKey key;
+ TextFreq *searchres;
+ Selectivity s1, s2;
+
+ /* since this function recurses, it could be driven to stack overflow */
+ check_stack_depth();
+
+ if (item->type == QI_VAL)
+ {
+ QueryOperand *oper = (QueryOperand *) item;
+
+ /*
+ * Prepare the key for bsearch().
+ */
+ key.lexeme = operand + oper->distance;
+ key.length = oper->length;
+
+ searchres = (TextFreq *) bsearch(&key, lookup, length,
+
sizeof(TextFreq), compare_lexeme_textfreq);
+ if (searchres)
+ {
+ /*
+ * The element is in MCELEM. Return precise selectivity
(or at
+ * least as precise, as ANALYZE could find out).
+ */
+ return (Selectivity) searchres->frequency;
+ }
+ else
+ {
+ /*
+ * The element is not in MCELEM. Punt, but assure that
the
+ * selectivity cannot be more than minfreq / 2.
+ */
+ return (Selectivity) Min(DEFAULT_TS_SEL, minfreq / 2);
+ }
+ }
+
+ /* Current TSQuery node is an operator */
+ switch (item->operator.oper)
+ {
+ case OP_NOT:
+ return 1.0 - tsquery_opr_selec(item + 1, operand,
lookup,
+
length, minfreq);
+
+ case OP_AND:
+ return
+ tsquery_opr_selec(item + 1, operand, lookup,
length, minfreq) *
+ tsquery_opr_selec(item + item->operator.left,
operand, lookup,
+ length,
minfreq);
+
+ case OP_OR:
+ s1 = tsquery_opr_selec(item + 1, operand, lookup,
length, minfreq);
+ s2 = tsquery_opr_selec(item + item->operator.left,
operand, lookup,
+ length,
minfreq);
+ return s1 + s2 - s1 * s2;
+
+ default:
+ elog(ERROR, "unrecognized operator: %d",
item->operator.oper);
+ }
+
+ /* never reached, keep compiler happy */
+ return (Selectivity) DEFAULT_TS_SEL;
+ }
+
+ /*
+ * Traverse the tsquery preorder, calculating selectivity as:
+ *
+ * selec(left_oper) * selec(right_oper) in AND nodes,
+ *
+ * selec(left_oper) + selec(right_oper) -
+ * selec(left_oper) * selec(right_oper) in OR nodes,
+ *
+ * 1 - select(oper) in NOT nodes
+ *
+ * freq[val] in VAL nodes, if the value is in MCELEM
+ * min(freq[MCELEM]) / 2 in VAL nodes, if it is not
+ *
+ *
+ * Implementation-wise, we sort the MCELEM array to use binary
+ * search on it.
+ */
+ static Selectivity
+ mcelem_tsquery_selec(TSQuery query, Datum *mcelem, int nmcelem,
+ float4 *numbers, int
nnumbers)
+ {
+ float4 minfreq;
+ TextFreq *lookup;
+ Selectivity selec;
+ int i;
+
+ /* Grab the lowest frequency */
+ minfreq = numbers[nnumbers - 1];
+
+ /* Construct the array to be qsort()'ed */
+ Assert(nmcelem == nnumbers);
+ lookup = (TextFreq *) palloc(sizeof(TextFreq) * nmcelem);
+ for (i = 0; i < nmcelem; i++)
+ {
+ lookup[i].element = mcelem[i];
+ lookup[i].frequency = numbers[i];
+ }
+
+ qsort(lookup, nmcelem, sizeof(TextFreq), compare_two_textfreqs);
+
+ selec = tsquery_opr_selec(GETQUERY(query), GETOPERAND(query), lookup,
+ nmcelem, minfreq);
+
+ pfree(lookup);
+
+ return selec;
+ }
+
+ /*
+ * qsort() comparator for TextFreqs array. Sorts on the text datum.
+ * The comparision is byte-by-byte, because we already consider text datums
+ * equal only if their binary representations are equal and we don't really
+ * care about the result ordering, as long as it's the same as the one
+ * assumed by the bsearch() comparator.
+ */
+ static int
+ compare_two_textfreqs(const void *e1, const void *e2)
+ {
+ const TextFreq *t1 = (const TextFreq *) e1;
+ const TextFreq *t2 = (const TextFreq *) e2;
+
+ return DatumGetInt32(DirectFunctionCall2(bttext_pattern_cmp,
+
t1->element, t2->element));
+ }
+
+ /*
+ * bsearch() comparator for a lexeme (non-NULL terminated string with length)
+ * and a TextFreq. Use byte-for-byte comparision, because that's the one we
+ * qsort()ed on.
+ */
+ static int
+ compare_lexeme_textfreq(const void *e1, const void *e2)
+ {
+ const LexemeKey *key;
+ const TextFreq *t;
+ text *element;
+ int result;
+ int len1,
+ len2;
+
+ key = (const LexemeKey *) e1;
+ t = (const TextFreq *) e2;
+ element = DatumGetTextP(t->element);
+
+ len1 = key->length;
+ len2 = VARSIZE_ANY_EXHDR(element);
+
+ result = strncmp(key->lexeme, VARDATA_ANY(element), Min(len1, len2));
+
+ if (result != 0)
+ return result;
+ else if (len1 < len2)
+ return -1;
+ else if (len1 > len2)
+ return 1;
+ else
+ return 0;
+ }
+
+ /*
+ * tssel -- Selectivity of "@@"
+ */
+ Datum
+ tssel(PG_FUNCTION_ARGS)
+ {
+ PlannerInfo *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+ /* We skip arg #2, which is the operator OID - it's gonna be "@@" */
+ List *args = (List *) PG_GETARG_POINTER(2);
+ int varRelid = PG_GETARG_INT32(3);
+ VariableStatData vardata;
+ Node *other;
+ bool varonleft;
+ Selectivity selec;
+
+ /*
+ * If expression is not variable op something or something op variable,
+ * then punt and return a default estimate.
+ */
+ if (!get_restriction_variable(root, args, varRelid,
+ &vardata,
&other, &varonleft))
+ {
+ PG_RETURN_FLOAT8(DEFAULT_TS_SEL);
+ }
+
+ /*
+ * Can't do anything useful if the something is not a constant, either.
+ */
+ if (!IsA(other, Const))
+ {
+ ReleaseVariableStats(vardata);
+ PG_RETURN_FLOAT8(DEFAULT_TS_SEL);
+ }
+
+ /* The "@@" operator is strict, so might cope with NULL right away */
+ if (((Const *) other)->constisnull) {
+ ReleaseVariableStats(vardata);
+ PG_RETURN_FLOAT8((float8) 0.0);
+ }
+
+ /*
+ * OK, there's a Var and a Const we're dealing with here. We need the
Var
+ * to be a TSVector (or else we don't have any useful statistic for it).
+ */
+
+ if (vardata.vartype == TSVECTOROID)
+ {
+ /* tsvector @@ tsquery or the other way around */
+ Assert(((Const *) other)->consttype == TSQUERYOID);
+
+ selec = tsquerysel(&vardata, ((Const *) other)->constvalue);
+ }
+ else
+ {
+ /* The Var is something we don't have useful statistic for */
+ selec = DEFAULT_TS_SEL;
+ }
+
+ ReleaseVariableStats(vardata);
+
+ PG_RETURN_FLOAT8((float8) selec);
+ }
+
+ static Selectivity
+ tsquerysel(VariableStatData *vardata, Datum constval)
+ {
+ Selectivity selec;
+
+ if (HeapTupleIsValid(vardata->statsTuple))
+ {
+ TSQuery query;
+ Form_pg_statistic stats;
+ Datum *values;
+ int nvalues;
+ float4 *numbers;
+ int nnumbers;
+
+ /* The caller made sure the const is a TSQuery, so get it now */
+ query = DatumGetTSQuery(constval);
+
+ stats = (Form_pg_statistic) GETSTRUCT(vardata->statsTuple);
+
+ /* MCELEM will be an array of Text elements for a tsvector
column */
+ if (get_attstatsslot(vardata->statsTuple,
+ TEXTOID, -1,
+ STATISTIC_KIND_MCELEM,
InvalidOid,
+ &values, &nvalues,
+ &numbers, &nnumbers))
+ {
+ /*
+ * There is a most-common-elements slot for the
tsvector Var, so
+ * use that.
+ */
+
+ selec = mcelem_tsquery_selec(query, values, nvalues,
+
numbers, nnumbers);
+ free_attstatsslot(TEXTOID, values, nvalues, numbers,
nnumbers);
+ }
+ else
+ {
+ /* No most-common-elements slot */
+ selec = (Selectivity) DEFAULT_TS_SEL;
+ }
+ }
+ else
+ {
+ selec = (Selectivity) DEFAULT_TS_SEL;
+ }
+
+ return selec;
+ }
diff --git a/src/include/catalog/pg_operator.h
b/src/include/catalog/pg_operator.h
index 1c7f37d..451805d 100644
*** a/src/include/catalog/pg_operator.h
--- b/src/include/catalog/pg_operator.h
***************
*** 915,924 ****
DATA(insert OID = 3631 ( ">=" PGNSP PGUID b f f 3614 3614
16 3628 3627 tsvector_ge scalargtsel scalargtjoinsel ));
DATA(insert OID = 3632 ( ">" PGNSP PGUID b f f 3614 3614 16
3627 3628 tsvector_gt scalargtsel scalargtjoinsel ));
DATA(insert OID = 3633 ( "||" PGNSP PGUID b f f 3614 3614
3614 0 0 tsvector_concat - - ));
! DATA(insert OID = 3636 ( "@@" PGNSP PGUID b f f 3614 3615
16 3637 0 ts_match_vq contsel contjoinsel ));
! DATA(insert OID = 3637 ( "@@" PGNSP PGUID b f f 3615 3614
16 3636 0 ts_match_qv contsel contjoinsel ));
! DATA(insert OID = 3660 ( "@@@" PGNSP PGUID b f f 3614 3615 16
3661 0 ts_match_vq contsel contjoinsel ));
! DATA(insert OID = 3661 ( "@@@" PGNSP PGUID b f f 3615 3614 16
3660 0 ts_match_qv contsel contjoinsel ));
DATA(insert OID = 3674 ( "<" PGNSP PGUID b f f 3615 3615 16
3679 3678 tsquery_lt scalarltsel scalarltjoinsel ));
DATA(insert OID = 3675 ( "<=" PGNSP PGUID b f f 3615 3615
16 3678 3679 tsquery_le scalarltsel scalarltjoinsel ));
DATA(insert OID = 3676 ( "=" PGNSP PGUID b t f 3615 3615 16
3676 3677 tsquery_eq eqsel eqjoinsel ));
--- 915,924 ----
DATA(insert OID = 3631 ( ">=" PGNSP PGUID b f f 3614 3614
16 3628 3627 tsvector_ge scalargtsel scalargtjoinsel ));
DATA(insert OID = 3632 ( ">" PGNSP PGUID b f f 3614 3614 16
3627 3628 tsvector_gt scalargtsel scalargtjoinsel ));
DATA(insert OID = 3633 ( "||" PGNSP PGUID b f f 3614 3614
3614 0 0 tsvector_concat - - ));
! DATA(insert OID = 3636 ( "@@" PGNSP PGUID b f f 3614 3615
16 3637 0 ts_match_vq tssel contjoinsel ));
! DATA(insert OID = 3637 ( "@@" PGNSP PGUID b f f 3615 3614
16 3636 0 ts_match_qv tssel contjoinsel ));
! DATA(insert OID = 3660 ( "@@@" PGNSP PGUID b f f 3614 3615 16
3661 0 ts_match_vq tssel contjoinsel ));
! DATA(insert OID = 3661 ( "@@@" PGNSP PGUID b f f 3615 3614 16
3660 0 ts_match_qv tssel contjoinsel ));
DATA(insert OID = 3674 ( "<" PGNSP PGUID b f f 3615 3615 16
3679 3678 tsquery_lt scalarltsel scalarltjoinsel ));
DATA(insert OID = 3675 ( "<=" PGNSP PGUID b f f 3615 3615
16 3678 3679 tsquery_le scalarltsel scalarltjoinsel ));
DATA(insert OID = 3676 ( "=" PGNSP PGUID b t f 3615 3615 16
3676 3677 tsquery_eq eqsel eqjoinsel ));
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 16ccb55..ef24f40 100644
*** a/src/include/catalog/pg_proc.h
--- b/src/include/catalog/pg_proc.h
***************
*** 4321,4326 ****
--- 4321,4328 ----
DATA(insert OID = 3701 ( gtsquery_consistent PGNSP PGUID 12
1 0 0 f f t f i 5 16 "2281 2281 23 26 2281" _null_ _null_ _null_
gtsquery_consistent _null_ _null_ _null_ ));
DESCR("GiST tsquery support");
+ DATA(insert OID = 3687 ( tssel PGNSP PGUID 12 1 0 0 f f t f s 4 701
"2281 26 2281 23" _null_ _null_ _null_ tssel _null_ _null_ _null_ ));
+ DESCR("restriction selectivity of tsvector @@ tsquery");
DATA(insert OID = 3688 ( ts_typanalyze PGNSP PGUID 12 1 0 0 f f t f s
1 16 "2281" _null_ _null_ _null_ ts_typanalyze _null_ _null_ _null_ ));
DESCR("tsvector typanalyze");
diff --git a/src/include/tsearch/ts_type.h b/src/include/tsearch/ts_type.h
index 06ca1f9..b253327 100644
*** a/src/include/tsearch/ts_type.h
--- b/src/include/tsearch/ts_type.h
***************
*** 155,160 ****
--- 155,162 ----
extern Datum ts_typanalyze(PG_FUNCTION_ARGS);
+ extern Datum tssel(PG_FUNCTION_ARGS);
+
/*
* TSQuery
***************
*** 291,294 ****
--- 293,309 ----
extern Datum tsq_mcontains(PG_FUNCTION_ARGS);
extern Datum tsq_mcontained(PG_FUNCTION_ARGS);
+ /*
+ * The default text search selectivity is chosen to be smll enough to
+ * encourage indexscans for typical table densities. See selfuncs.h and
+ * DEFAULT_EQ_SEL for details.
+ */
+ #define DEFAULT_TS_SEL 0.005
+
+ /*
+ * operator restriction function for tsvector @@ tsquery and
+ * tsquery @@ tsvector
+ */
+ extern Datum tssel(PG_FUNCTION_ARGS);
+
#endif /* _PG_TSTYPE_H_ */
--
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