Add analyze.c file for split.

26 years ago · f089c36419
parent 35096b568e
commit f089c36419
1 changed files with 635 additions and 0 deletions
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@ -0,0 +1,635 @@
+/*-------------------------------------------------------------------------
+ *
+ * analyze.c
+ *	  the postgres optimizer analyzer
+ *
+ * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/analyze.c,v 1.1 2000/05/29 17:44:17 momjian Exp $
+ *
+
+ *-------------------------------------------------------------------------
+ */
+#include <sys/types.h>
+#include <sys/file.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "postgres.h"
+
+#include "access/heapam.h"
+#include "catalog/catname.h"
+#include "catalog/indexing.h"
+#include "catalog/pg_operator.h"
+#include "catalog/pg_statistic.h"
+#include "catalog/pg_type.h"
+#include "commands/vacuum.h"
+#include "miscadmin.h"
+#include "parser/parse_oper.h"
+#include "tcop/tcopprot.h"
+#include "utils/acl.h"
+#include "utils/builtins.h"
+#include "utils/fmgroids.h"
+#include "utils/inval.h"
+#include "utils/syscache.h"
+
+#define swapLong(a,b)	{long tmp; tmp=a; a=b; b=tmp;}
+#define swapInt(a,b)	{int tmp; tmp=a; a=b; b=tmp;}
+#define swapDatum(a,b)	{Datum tmp; tmp=a; a=b; b=tmp;}
+#define VacAttrStatsEqValid(stats) ( stats->f_cmpeq.fn_addr != NULL )
+#define VacAttrStatsLtGtValid(stats) ( stats->f_cmplt.fn_addr != NULL && \
+								   stats->f_cmpgt.fn_addr != NULL && \
+								   RegProcedureIsValid(stats->outfunc) )
+
+
+static void attr_stats(Relation onerel, int attr_cnt, VacAttrStats *vacattrstats, HeapTuple tuple);
+static void bucketcpy(Form_pg_attribute attr, Datum value, Datum *bucket, int *bucket_len);
+static void update_attstats(Oid relid, int natts, VacAttrStats *vacattrstats);
+static void del_stats(Oid relid, int attcnt, int *attnums);
+
+
+/*
+ *	analyze_rel() -- analyze relation
+ */
+void
+analyze_rel(Oid relid, List *anal_cols2, int MESSAGE_LEVEL)
+{
+	HeapTuple	tuple,
+				typetuple;
+	Relation	onerel;
+	int32		i;
+	int			attr_cnt,
+			   *attnums = NULL;
+	Form_pg_attribute *attr;
+	VacAttrStats *vacattrstats;
+	HeapScanDesc scan;
+
+	StartTransactionCommand();
+
+	/*
+	 * Check for user-requested abort.	Note we want this to be inside a
+	 * transaction, so xact.c doesn't issue useless NOTICE.
+	 */
+	if (QueryCancel)
+		CancelQuery();
+
+	/*
+	 * Race condition -- if the pg_class tuple has gone away since the
+	 * last time we saw it, we don't need to vacuum it.
+	 */
+	tuple = SearchSysCacheTuple(RELOID,
+								ObjectIdGetDatum(relid),
+								0, 0, 0);
+	/*
+	 * We can VACUUM ANALYZE any table except pg_statistic.
+	 * see update_relstats
+	 */
+	if (!HeapTupleIsValid(tuple) ||
+		strcmp(NameStr(((Form_pg_class) GETSTRUCT(tuple))->relname),
+				StatisticRelationName) == 0)
+	{
+		CommitTransactionCommand();
+		return;
+	}
+
+	onerel = heap_open(relid, AccessShareLock);
+
+#ifndef NO_SECURITY
+	if (!pg_ownercheck(GetPgUserName(), RelationGetRelationName(onerel),
+					   RELNAME))
+	{
+		/* we already did an elog during vacuum
+		elog(NOTICE, "Skipping \"%s\" --- only table owner can VACUUM it",
+			 RelationGetRelationName(onerel));
+		*/
+		heap_close(onerel, AccessExclusiveLock);
+		CommitTransactionCommand();
+		return;
+	}
+#endif
+
+	elog(MESSAGE_LEVEL, "Analyzing...");
+
+	attr_cnt = onerel->rd_att->natts;
+	attr = onerel->rd_att->attrs;
+
+	if (anal_cols2 != NIL)
+	{
+		int			tcnt = 0;
+		List	   *le;
+
+		if (length(anal_cols2) > attr_cnt)
+			elog(ERROR, "vacuum: too many attributes specified for relation %s",
+				 RelationGetRelationName(onerel));
+		attnums = (int *) palloc(attr_cnt * sizeof(int));
+		foreach(le, anal_cols2)
+		{
+			char	   *col = (char *) lfirst(le);
+
+			for (i = 0; i < attr_cnt; i++)
+			{
+				if (namestrcmp(&(attr[i]->attname), col) == 0)
+					break;
+			}
+			if (i < attr_cnt)		/* found */
+				attnums[tcnt++] = i;
+			else
+			{
+				elog(ERROR, "vacuum: there is no attribute %s in %s",
+					 col, RelationGetRelationName(onerel));
+			}
+		}
+		attr_cnt = tcnt;
+	}
+
+	vacattrstats = (VacAttrStats *) palloc(attr_cnt * sizeof(VacAttrStats));
+
+	for (i = 0; i < attr_cnt; i++)
+	{
+		Operator	func_operator;
+		Form_pg_operator pgopform;
+		VacAttrStats *stats;
+
+		stats = &vacattrstats[i];
+		stats->attr = palloc(ATTRIBUTE_TUPLE_SIZE);
+		memmove(stats->attr, attr[((attnums) ? attnums[i] : i)], ATTRIBUTE_TUPLE_SIZE);
+		stats->best = stats->guess1 = stats->guess2 = 0;
+		stats->max = stats->min = 0;
+		stats->best_len = stats->guess1_len = stats->guess2_len = 0;
+		stats->max_len = stats->min_len = 0;
+		stats->initialized = false;
+		stats->best_cnt = stats->guess1_cnt = stats->guess1_hits = stats->guess2_hits = 0;
+		stats->max_cnt = stats->min_cnt = stats->null_cnt = stats->nonnull_cnt = 0;
+
+		func_operator = oper("=", stats->attr->atttypid, stats->attr->atttypid, true);
+		if (func_operator != NULL)
+		{
+			pgopform = (Form_pg_operator) GETSTRUCT(func_operator);
+			fmgr_info(pgopform->oprcode, &(stats->f_cmpeq));
+		}
+		else
+			stats->f_cmpeq.fn_addr = NULL;
+
+		func_operator = oper("<", stats->attr->atttypid, stats->attr->atttypid, true);
+		if (func_operator != NULL)
+		{
+			pgopform = (Form_pg_operator) GETSTRUCT(func_operator);
+			fmgr_info(pgopform->oprcode, &(stats->f_cmplt));
+			stats->op_cmplt = oprid(func_operator);
+		}
+		else
+		{
+			stats->f_cmplt.fn_addr = NULL;
+			stats->op_cmplt = InvalidOid;
+		}
+
+		func_operator = oper(">", stats->attr->atttypid, stats->attr->atttypid, true);
+		if (func_operator != NULL)
+		{
+			pgopform = (Form_pg_operator) GETSTRUCT(func_operator);
+			fmgr_info(pgopform->oprcode, &(stats->f_cmpgt));
+		}
+		else
+			stats->f_cmpgt.fn_addr = NULL;
+
+		typetuple = SearchSysCacheTuple(TYPEOID,
+							 ObjectIdGetDatum(stats->attr->atttypid),
+										0, 0, 0);
+		if (HeapTupleIsValid(typetuple))
+		{
+			stats->outfunc = ((Form_pg_type) GETSTRUCT(typetuple))->typoutput;
+			stats->typelem = ((Form_pg_type) GETSTRUCT(typetuple))->typelem;
+		}
+		else
+		{
+			stats->outfunc = InvalidOid;
+			stats->typelem = InvalidOid;
+		}
+	}
+	/* delete existing pg_statistic rows for relation */
+	del_stats(relid, ((attnums) ? attr_cnt : 0), attnums);
+
+	scan = heap_beginscan(onerel, false, SnapshotNow, 0, NULL);
+
+	while (HeapTupleIsValid(tuple = heap_getnext(scan, 0)))
+		attr_stats(onerel, attr_cnt, vacattrstats, tuple);
+
+	heap_endscan(scan);
+
+	heap_close(onerel, AccessShareLock);
+
+	/* update statistics in pg_class */
+	update_attstats(relid, attr_cnt, vacattrstats);
+
+	CommitTransactionCommand();
+}
+
+/*
+ *	attr_stats() -- compute column statistics used by the optimzer
+ *
+ *	We compute the column min, max, null and non-null counts.
+ *	Plus we attempt to find the count of the value that occurs most
+ *	frequently in each column.	These figures are used to compute
+ *	the selectivity of the column.
+ *
+ *	We use a three-bucked cache to get the most frequent item.
+ *	The 'guess' buckets count hits.  A cache miss causes guess1
+ *	to get the most hit 'guess' item in the most recent cycle, and
+ *	the new item goes into guess2.	Whenever the total count of hits
+ *	of a 'guess' entry is larger than 'best', 'guess' becomes 'best'.
+ *
+ *	This method works perfectly for columns with unique values, and columns
+ *	with only two unique values, plus nulls.
+ *
+ *	It becomes less perfect as the number of unique values increases and
+ *	their distribution in the table becomes more random.
+ *
+ */
+static void
+attr_stats(Relation onerel, int attr_cnt, VacAttrStats *vacattrstats, HeapTuple tuple)
+{
+	int			i;
+	TupleDesc	tupDesc = onerel->rd_att;
+	Datum		value;
+	bool		isnull;
+
+	for (i = 0; i < attr_cnt; i++)
+	{
+		VacAttrStats *stats = &vacattrstats[i];
+		bool		value_hit = true;
+
+#ifdef	_DROP_COLUMN_HACK__
+		if (COLUMN_IS_DROPPED(stats->attr))
+			continue;
+#endif	 /* _DROP_COLUMN_HACK__ */
+		value = heap_getattr(tuple,
+							 stats->attr->attnum, tupDesc, &isnull);
+
+		if (!VacAttrStatsEqValid(stats))
+			continue;
+
+		if (isnull)
+			stats->null_cnt++;
+		else
+		{
+			stats->nonnull_cnt++;
+			if (stats->initialized == false)
+			{
+				bucketcpy(stats->attr, value, &stats->best, &stats->best_len);
+				/* best_cnt gets incremented later */
+				bucketcpy(stats->attr, value, &stats->guess1, &stats->guess1_len);
+				stats->guess1_cnt = stats->guess1_hits = 1;
+				bucketcpy(stats->attr, value, &stats->guess2, &stats->guess2_len);
+				stats->guess2_hits = 1;
+				if (VacAttrStatsLtGtValid(stats))
+				{
+					bucketcpy(stats->attr, value, &stats->max, &stats->max_len);
+					bucketcpy(stats->attr, value, &stats->min, &stats->min_len);
+				}
+				stats->initialized = true;
+			}
+			if (VacAttrStatsLtGtValid(stats))
+			{
+				if ((*fmgr_faddr(&stats->f_cmplt)) (value, stats->min))
+				{
+					bucketcpy(stats->attr, value, &stats->min, &stats->min_len);
+					stats->min_cnt = 0;
+				}
+				if ((*fmgr_faddr(&stats->f_cmpgt)) (value, stats->max))
+				{
+					bucketcpy(stats->attr, value, &stats->max, &stats->max_len);
+					stats->max_cnt = 0;
+				}
+				if ((*fmgr_faddr(&stats->f_cmpeq)) (value, stats->min))
+					stats->min_cnt++;
+				else if ((*fmgr_faddr(&stats->f_cmpeq)) (value, stats->max))
+					stats->max_cnt++;
+			}
+			if ((*fmgr_faddr(&stats->f_cmpeq)) (value, stats->best))
+				stats->best_cnt++;
+			else if ((*fmgr_faddr(&stats->f_cmpeq)) (value, stats->guess1))
+			{
+				stats->guess1_cnt++;
+				stats->guess1_hits++;
+			}
+			else if ((*fmgr_faddr(&stats->f_cmpeq)) (value, stats->guess2))
+				stats->guess2_hits++;
+			else
+				value_hit = false;
+
+			if (stats->guess2_hits > stats->guess1_hits)
+			{
+				swapDatum(stats->guess1, stats->guess2);
+				swapInt(stats->guess1_len, stats->guess2_len);
+				swapLong(stats->guess1_hits, stats->guess2_hits);
+				stats->guess1_cnt = stats->guess1_hits;
+			}
+			if (stats->guess1_cnt > stats->best_cnt)
+			{
+				swapDatum(stats->best, stats->guess1);
+				swapInt(stats->best_len, stats->guess1_len);
+				swapLong(stats->best_cnt, stats->guess1_cnt);
+				stats->guess1_hits = 1;
+				stats->guess2_hits = 1;
+			}
+			if (!value_hit)
+			{
+				bucketcpy(stats->attr, value, &stats->guess2, &stats->guess2_len);
+				stats->guess1_hits = 1;
+				stats->guess2_hits = 1;
+			}
+		}
+	}
+	return;
+}
+
+/*
+ *	bucketcpy() -- update pg_class statistics for one relation
+ *
+ */
+static void
+bucketcpy(Form_pg_attribute attr, Datum value, Datum *bucket, int *bucket_len)
+{
+	if (attr->attbyval && attr->attlen != -1)
+		*bucket = value;
+	else
+	{
+		int			len = (attr->attlen != -1 ? attr->attlen : VARSIZE(value));
+
+		if (len > *bucket_len)
+		{
+			if (*bucket_len != 0)
+				pfree(DatumGetPointer(*bucket));
+			*bucket = PointerGetDatum(palloc(len));
+			*bucket_len = len;
+		}
+		memmove(DatumGetPointer(*bucket), DatumGetPointer(value), len);
+	}
+}
+
+
+/*
+ *	update_attstats() -- update attribute statistics for one relation
+ *
+ *		Updates of pg_attribute statistics are handled by over-write.
+ *		for reasons described above.
+ *
+ *		To keep things simple, we punt for pg_statistic, and don't try
+ *		to compute or store rows for pg_statistic itself in pg_statistic.
+ *		This could possibly be made to work, but it's not worth the trouble.
+ */
+static void
+update_attstats(Oid relid, int natts, VacAttrStats *vacattrstats)
+{
+	Relation	ad,
+				sd;
+	HeapScanDesc scan;
+	HeapTuple	atup,
+				stup;
+	ScanKeyData askey;
+	Form_pg_attribute attp;
+
+	ad = heap_openr(AttributeRelationName, RowExclusiveLock);
+	sd = heap_openr(StatisticRelationName, RowExclusiveLock);
+
+	/* Find pg_attribute rows for this relation */
+	ScanKeyEntryInitialize(&askey, 0, Anum_pg_attribute_attrelid,
+						   F_INT4EQ, relid);
+
+	scan = heap_beginscan(ad, false, SnapshotNow, 1, &askey);
+
+	while (HeapTupleIsValid(atup = heap_getnext(scan, 0)))
+	{
+		int			i;
+		VacAttrStats *stats;
+
+		attp = (Form_pg_attribute) GETSTRUCT(atup);
+		if (attp->attnum <= 0)		/* skip system attributes for now */
+			continue;
+
+		for (i = 0; i < natts; i++)
+		{
+			if (attp->attnum == vacattrstats[i].attr->attnum)
+				break;
+		}
+		if (i >= natts)
+			continue;		/* skip attr if no stats collected */
+		stats = &(vacattrstats[i]);
+
+		if (VacAttrStatsEqValid(stats))
+		{
+			float32data selratio;	/* average ratio of rows selected
+									 * for a random constant */
+
+			/* Compute disbursion */
+			if (stats->nonnull_cnt == 0 && stats->null_cnt == 0)
+			{
+
+				/*
+				 * empty relation, so put a dummy value in
+				 * attdisbursion
+				 */
+				selratio = 0;
+			}
+			else if (stats->null_cnt <= 1 && stats->best_cnt == 1)
+			{
+				/*
+				 * looks like we have a unique-key attribute --- flag
+				 * this with special -1.0 flag value.
+				 *
+				 * The correct disbursion is 1.0/numberOfRows, but since
+				 * the relation row count can get updated without
+				 * recomputing disbursion, we want to store a
+				 * "symbolic" value and figure 1.0/numberOfRows on the
+				 * fly.
+				 */
+				selratio = -1;
+			}
+			else
+			{
+				if (VacAttrStatsLtGtValid(stats) &&
+				stats->min_cnt + stats->max_cnt == stats->nonnull_cnt)
+				{
+
+					/*
+					 * exact result when there are just 1 or 2
+					 * values...
+					 */
+					double		min_cnt_d = stats->min_cnt,
+								max_cnt_d = stats->max_cnt,
+								null_cnt_d = stats->null_cnt;
+					double		total = ((double) stats->nonnull_cnt) + null_cnt_d;
+
+					selratio = (min_cnt_d * min_cnt_d + max_cnt_d * max_cnt_d + null_cnt_d * null_cnt_d) / (total * total);
+				}
+				else
+				{
+					double		most = (double) (stats->best_cnt > stats->null_cnt ? stats->best_cnt : stats->null_cnt);
+					double		total = ((double) stats->nonnull_cnt) + ((double) stats->null_cnt);
+
+					/*
+					 * we assume count of other values are 20% of best
+					 * count in table
+					 */
+					selratio = (most * most + 0.20 * most * (total - most)) / (total * total);
+				}
+				/* Make sure calculated values are in-range */
+				if (selratio < 0.0)
+					selratio = 0.0;
+				else if (selratio > 1.0)
+					selratio = 1.0;
+			}
+
+			/* overwrite the existing statistics in the tuple */
+			attp->attdisbursion = selratio;
+
+			/* invalidate the tuple in the cache and write the buffer */
+			RelationInvalidateHeapTuple(ad, atup);
+			WriteNoReleaseBuffer(scan->rs_cbuf);
+
+			/*
+			 * Create pg_statistic tuples for the relation, if we have
+			 * gathered the right data.  del_stats() previously
+			 * deleted all the pg_statistic tuples for the rel, so we
+			 * just have to insert new ones here.
+			 *
+			 * Note vacuum_rel() has seen to it that we won't come here
+			 * when vacuuming pg_statistic itself.
+			 */
+			if (VacAttrStatsLtGtValid(stats) && stats->initialized)
+			{
+				float32data nullratio;
+				float32data bestratio;
+				FmgrInfo	out_function;
+				char	   *out_string;
+				double		best_cnt_d = stats->best_cnt,
+							null_cnt_d = stats->null_cnt,
+							nonnull_cnt_d = stats->nonnull_cnt;		/* prevent overflow */
+				Datum		values[Natts_pg_statistic];
+				char		nulls[Natts_pg_statistic];
+
+				nullratio = null_cnt_d / (nonnull_cnt_d + null_cnt_d);
+				bestratio = best_cnt_d / (nonnull_cnt_d + null_cnt_d);
+
+				fmgr_info(stats->outfunc, &out_function);
+
+				for (i = 0; i < Natts_pg_statistic; ++i)
+					nulls[i] = ' ';
+
+				/* ----------------
+				 *	initialize values[]
+				 * ----------------
+				 */
+				i = 0;
+				values[i++] = (Datum) relid;		/* starelid */
+				values[i++] = (Datum) attp->attnum; /* staattnum */
+				values[i++] = (Datum) stats->op_cmplt;		/* staop */
+				/* hack: this code knows float4 is pass-by-ref */
+				values[i++] = PointerGetDatum(&nullratio);	/* stanullfrac */
+				values[i++] = PointerGetDatum(&bestratio);	/* stacommonfrac */
+				out_string = (*fmgr_faddr(&out_function)) (stats->best, stats->typelem, stats->attr->atttypmod);
+				values[i++] = PointerGetDatum(textin(out_string));	/* stacommonval */
+				pfree(out_string);
+				out_string = (*fmgr_faddr(&out_function)) (stats->min, stats->typelem, stats->attr->atttypmod);
+				values[i++] = PointerGetDatum(textin(out_string));	/* staloval */
+				pfree(out_string);
+				out_string = (char *) (*fmgr_faddr(&out_function)) (stats->max, stats->typelem, stats->attr->atttypmod);
+				values[i++] = PointerGetDatum(textin(out_string));	/* stahival */
+				pfree(out_string);
+
+				stup = heap_formtuple(sd->rd_att, values, nulls);
+
+				/* ----------------
+				 *	Watch out for oversize tuple, which can happen if
+				 *	all three of the saved data values are long.
+				 *	Our fallback strategy is just to not store the
+				 *	pg_statistic tuple at all in that case.  (We could
+				 *	replace the values by NULLs and still store the
+				 *	numeric stats, but presently selfuncs.c couldn't
+				 *	do anything useful with that case anyway.)
+				 *
+				 *	We could reduce the probability of overflow, but not
+				 *	prevent it, by storing the data values as compressed
+				 *	text; is that worth doing?	The problem should go
+				 *	away whenever long tuples get implemented...
+				 * ----------------
+				 */
+				if (MAXALIGN(stup->t_len) <= MaxTupleSize)
+				{
+					/* OK, store tuple and update indexes too */
+					Relation	irelations[Num_pg_statistic_indices];
+
+					heap_insert(sd, stup);
+					CatalogOpenIndices(Num_pg_statistic_indices, Name_pg_statistic_indices, irelations);
+					CatalogIndexInsert(irelations, Num_pg_statistic_indices, sd, stup);
+					CatalogCloseIndices(Num_pg_statistic_indices, irelations);
+				}
+
+				/* release allocated space */
+				pfree(DatumGetPointer(values[Anum_pg_statistic_stacommonval - 1]));
+				pfree(DatumGetPointer(values[Anum_pg_statistic_staloval - 1]));
+				pfree(DatumGetPointer(values[Anum_pg_statistic_stahival - 1]));
+				heap_freetuple(stup);
+			}
+		}
+	}
+	heap_endscan(scan);
+	/* close rels, but hold locks till upcoming commit */
+	heap_close(ad, NoLock);
+	heap_close(sd, NoLock);
+}
+
+/*
+ *	del_stats() -- delete pg_statistic rows for a relation
+ *
+ *	If a list of attribute numbers is given, only zap stats for those attrs.
+ */
+static void
+del_stats(Oid relid, int attcnt, int *attnums)
+{
+	Relation	pgstatistic;
+	HeapScanDesc scan;
+	HeapTuple	tuple;
+	ScanKeyData key;
+
+	pgstatistic = heap_openr(StatisticRelationName, RowExclusiveLock);
+
+	ScanKeyEntryInitialize(&key, 0x0, Anum_pg_statistic_starelid,
+						   F_OIDEQ, ObjectIdGetDatum(relid));
+	scan = heap_beginscan(pgstatistic, false, SnapshotNow, 1, &key);
+
+	while (HeapTupleIsValid(tuple = heap_getnext(scan, 0)))
+	{
+		if (attcnt > 0)
+		{
+			Form_pg_statistic pgs = (Form_pg_statistic) GETSTRUCT(tuple);
+			int			i;
+
+			for (i = 0; i < attcnt; i++)
+			{
+				if (pgs->staattnum == attnums[i] + 1)
+					break;
+			}
+			if (i >= attcnt)
+				continue;		/* don't delete it */
+		}
+		heap_delete(pgstatistic, &tuple->t_self, NULL);
+	}
+
+	heap_endscan(scan);
+
+	/*
+	 * Close rel, but *keep* lock; we will need to reacquire it later, so
+	 * there's a possibility of deadlock against another VACUUM process if
+	 * we let go now.  Keeping the lock shouldn't delay any common
+	 * operation other than an attempted VACUUM of pg_statistic itself.
+	 */
+	heap_close(pgstatistic, NoLock);
+}
+
+
+