Take pg_attribute out of VacAttrStats

The VacAttrStats structure contained the whole Form_pg_attribute for a
column, but it actually only needs attstattarget from there.  So
remove the Form_pg_attribute field and make a separate field for
attstattarget.  This simplifies some code for extended statistics that
doesn't deal with a column but an expression, which had to fake up
pg_attribute rows to satisfy internal APIs.  Also, we can remove some
comments that essentially said "don't look at pg_attribute directly".

Reviewed-by: Tomas Vondra <tomas.vondra@enterprisedb.com>
Discussion: https://www.postgresql.org/message-id/flat/d6069765-5971-04d3-c10d-e4f7b2e9c459%40eisentraut.org

Author: petere

src/backend/commands/analyze.c

@@ -572,7 +572,7 @@ do_analyze_rel(Relation onerel, VacuumParams *params,
 			 * If the appropriate flavor of the n_distinct option is
 			 * specified, override with the corresponding value.
 			 */
-			aopt = get_attribute_options(onerel->rd_id, stats->attr->attnum);
+			aopt = get_attribute_options(onerel->rd_id, stats->tupattnum);
 			if (aopt != NULL)
 			{
 				float8		n_distinct;
@@ -927,7 +927,7 @@ compute_index_stats(Relation onerel, double totalrows,
 				for (i = 0; i < attr_cnt; i++)
 				{
 					VacAttrStats *stats = thisdata->vacattrstats[i];
-					int			attnum = stats->attr->attnum;
+					int			attnum = stats->tupattnum;
 
 					if (isnull[attnum - 1])
 					{
@@ -1014,12 +1014,10 @@ examine_attribute(Relation onerel, int attnum, Node *index_expr)
 		return NULL;
 
 	/*
-	 * Create the VacAttrStats struct.  Note that we only have a copy of the
-	 * fixed fields of the pg_attribute tuple.
+	 * Create the VacAttrStats struct.
 	 */
 	stats = (VacAttrStats *) palloc0(sizeof(VacAttrStats));
-	stats->attr = (Form_pg_attribute) palloc(ATTRIBUTE_FIXED_PART_SIZE);
-	memcpy(stats->attr, attr, ATTRIBUTE_FIXED_PART_SIZE);
+	stats->attstattarget = attr->attstattarget;
 
 	/*
 	 * When analyzing an expression index, believe the expression tree's type
@@ -1086,7 +1084,6 @@ examine_attribute(Relation onerel, int attnum, Node *index_expr)
 	if (!ok || stats->compute_stats == NULL || stats->minrows <= 0)
 	{
 		heap_freetuple(typtuple);
-		pfree(stats->attr);
 		pfree(stats);
 		return NULL;
 	}
@@ -1659,7 +1656,7 @@ update_attstats(Oid relid, bool inh, int natts, VacAttrStats **vacattrstats)
 		}
 
 		values[Anum_pg_statistic_starelid - 1] = ObjectIdGetDatum(relid);
-		values[Anum_pg_statistic_staattnum - 1] = Int16GetDatum(stats->attr->attnum);
+		values[Anum_pg_statistic_staattnum - 1] = Int16GetDatum(stats->tupattnum);
 		values[Anum_pg_statistic_stainherit - 1] = BoolGetDatum(inh);
 		values[Anum_pg_statistic_stanullfrac - 1] = Float4GetDatum(stats->stanullfrac);
 		values[Anum_pg_statistic_stawidth - 1] = Int32GetDatum(stats->stawidth);
@@ -1725,7 +1722,7 @@ update_attstats(Oid relid, bool inh, int natts, VacAttrStats **vacattrstats)
 		/* Is there already a pg_statistic tuple for this attribute? */
 		oldtup = SearchSysCache3(STATRELATTINH,
 								 ObjectIdGetDatum(relid),
-								 Int16GetDatum(stats->attr->attnum),
+								 Int16GetDatum(stats->tupattnum),
 								 BoolGetDatum(inh));
 
 		/* Open index information when we know we need it */
@@ -1860,15 +1857,13 @@ static int	analyze_mcv_list(int *mcv_counts,
 bool
 std_typanalyze(VacAttrStats *stats)
 {
-	Form_pg_attribute attr = stats->attr;
 	Oid			ltopr;
 	Oid			eqopr;
 	StdAnalyzeData *mystats;
 
 	/* If the attstattarget column is negative, use the default value */
-	/* NB: it is okay to scribble on stats->attr since it's a copy */
-	if (attr->attstattarget < 0)
-		attr->attstattarget = default_statistics_target;
+	if (stats->attstattarget < 0)
+		stats->attstattarget = default_statistics_target;
 
 	/* Look for default "<" and "=" operators for column's type */
 	get_sort_group_operators(stats->attrtypid,
@@ -1909,21 +1904,21 @@ std_typanalyze(VacAttrStats *stats)
 		 * know it at this point.
 		 *--------------------
 		 */
-		stats->minrows = 300 * attr->attstattarget;
+		stats->minrows = 300 * stats->attstattarget;
 	}
 	else if (OidIsValid(eqopr))
 	{
 		/* We can still recognize distinct values */
 		stats->compute_stats = compute_distinct_stats;
 		/* Might as well use the same minrows as above */
-		stats->minrows = 300 * attr->attstattarget;
+		stats->minrows = 300 * stats->attstattarget;
 	}
 	else
 	{
 		/* Can't do much but the trivial stuff */
 		stats->compute_stats = compute_trivial_stats;
 		/* Might as well use the same minrows as above */
-		stats->minrows = 300 * attr->attstattarget;
+		stats->minrows = 300 * stats->attstattarget;
 	}
 
 	return true;
@@ -2051,7 +2046,7 @@ compute_distinct_stats(VacAttrStatsP stats,
 	TrackItem  *track;
 	int			track_cnt,
 				track_max;
-	int			num_mcv = stats->attr->attstattarget;
+	int			num_mcv = stats->attstattarget;
 	StdAnalyzeData *mystats = (StdAnalyzeData *) stats->extra_data;
 
 	/*
@@ -2392,8 +2387,8 @@ compute_scalar_stats(VacAttrStatsP stats,
 	int		   *tupnoLink;
 	ScalarMCVItem *track;
 	int			track_cnt = 0;
-	int			num_mcv = stats->attr->attstattarget;
-	int			num_bins = stats->attr->attstattarget;
+	int			num_mcv = stats->attstattarget;
+	int			num_bins = stats->attstattarget;
 	StdAnalyzeData *mystats = (StdAnalyzeData *) stats->extra_data;
 
 	values = (ScalarItem *) palloc(samplerows * sizeof(ScalarItem));

src/backend/statistics/extended_stats.c

@@ -366,8 +366,8 @@ statext_compute_stattarget(int stattarget, int nattrs, VacAttrStats **stats)
 	for (i = 0; i < nattrs; i++)
 	{
 		/* keep the maximum statistics target */
-		if (stats[i]->attr->attstattarget > stattarget)
-			stattarget = stats[i]->attr->attstattarget;
+		if (stats[i]->attstattarget > stattarget)
+			stattarget = stats[i]->attstattarget;
 	}
 
 	/*
@@ -534,14 +534,10 @@ examine_attribute(Node *expr)
 	bool		ok;
 
 	/*
-	 * Create the VacAttrStats struct.  Note that we only have a copy of the
-	 * fixed fields of the pg_attribute tuple.
+	 * Create the VacAttrStats struct.
 	 */
 	stats = (VacAttrStats *) palloc0(sizeof(VacAttrStats));
-
-	/* fake the attribute */
-	stats->attr = (Form_pg_attribute) palloc0(ATTRIBUTE_FIXED_PART_SIZE);
-	stats->attr->attstattarget = -1;
+	stats->attstattarget = -1;
 
 	/*
 	 * When analyzing an expression, believe the expression tree's type not
@@ -595,7 +591,6 @@ examine_attribute(Node *expr)
 	if (!ok || stats->compute_stats == NULL || stats->minrows <= 0)
 	{
 		heap_freetuple(typtuple);
-		pfree(stats->attr);
 		pfree(stats);
 		return NULL;
 	}
@@ -624,6 +619,13 @@ examine_expression(Node *expr, int stattarget)
 	 */
 	stats = (VacAttrStats *) palloc0(sizeof(VacAttrStats));
 
+	/*
+	 * We can't have statistics target specified for the expression, so we
+	 * could use either the default_statistics_target, or the target computed
+	 * for the extended statistics. The second option seems more reasonable.
+	 */
+	stats->attstattarget = stattarget;
+
 	/*
 	 * When analyzing an expression, believe the expression tree's type.
 	 */
@@ -638,25 +640,6 @@ examine_expression(Node *expr, int stattarget)
 	 */
 	stats->attrcollid = exprCollation(expr);
 
-	/*
-	 * We don't have any pg_attribute for expressions, so let's fake something
-	 * reasonable into attstattarget, which is the only thing std_typanalyze
-	 * needs.
-	 */
-	stats->attr = (Form_pg_attribute) palloc(ATTRIBUTE_FIXED_PART_SIZE);
-
-	/*
-	 * We can't have statistics target specified for the expression, so we
-	 * could use either the default_statistics_target, or the target computed
-	 * for the extended statistics. The second option seems more reasonable.
-	 */
-	stats->attr->attstattarget = stattarget;
-
-	/* initialize some basic fields */
-	stats->attr->attrelid = InvalidOid;
-	stats->attr->attnum = InvalidAttrNumber;
-	stats->attr->atttypid = stats->attrtypid;
-
 	typtuple = SearchSysCacheCopy1(TYPEOID,
 								   ObjectIdGetDatum(stats->attrtypid));
 	if (!HeapTupleIsValid(typtuple))
@@ -747,12 +730,6 @@ lookup_var_attr_stats(Relation rel, Bitmapset *attrs, List *exprs,
 			return NULL;
 		}
 
-		/*
-		 * Sanity check that the column is not dropped - stats should have
-		 * been removed in this case.
-		 */
-		Assert(!stats[i]->attr->attisdropped);
-
 		i++;
 	}
 
@@ -2237,8 +2214,7 @@ compute_expr_stats(Relation onerel, double totalrows,
 		if (tcnt > 0)
 		{
 			AttributeOpts *aopt =
-				get_attribute_options(stats->attr->attrelid,
-									  stats->attr->attnum);
+				get_attribute_options(onerel->rd_id, stats->tupattnum);
 
 			stats->exprvals = exprvals;
 			stats->exprnulls = exprnulls;

src/backend/tsearch/ts_typanalyze.c

@@ -58,16 +58,14 @@ Datum
 ts_typanalyze(PG_FUNCTION_ARGS)
 {
 	VacAttrStats *stats = (VacAttrStats *) PG_GETARG_POINTER(0);
-	Form_pg_attribute attr = stats->attr;
 
 	/* If the attstattarget column is negative, use the default value */
-	/* NB: it is okay to scribble on stats->attr since it's a copy */
-	if (attr->attstattarget < 0)
-		attr->attstattarget = default_statistics_target;
+	if (stats->attstattarget < 0)
+		stats->attstattarget = default_statistics_target;
 
 	stats->compute_stats = compute_tsvector_stats;
 	/* see comment about the choice of minrows in commands/analyze.c */
-	stats->minrows = 300 * attr->attstattarget;
+	stats->minrows = 300 * stats->attstattarget;
 
 	PG_RETURN_BOOL(true);
 }
@@ -169,7 +167,7 @@ compute_tsvector_stats(VacAttrStats *stats,
 	 * the number of individual lexeme values tracked in pg_statistic ought to
 	 * be more than the number of values for a simple scalar column.
 	 */
-	num_mcelem = stats->attr->attstattarget * 10;
+	num_mcelem = stats->attstattarget * 10;
 
 	/*
 	 * We set bucket width equal to (num_mcelem + 10) / 0.007 as per the

src/backend/utils/adt/array_typanalyze.c

@@ -263,7 +263,7 @@ compute_array_stats(VacAttrStats *stats, AnalyzeAttrFetchFunc fetchfunc,
 	 * the number of individual elements tracked in pg_statistic ought to be
 	 * more than the number of values for a simple scalar column.
 	 */
-	num_mcelem = stats->attr->attstattarget * 10;
+	num_mcelem = stats->attstattarget * 10;
 
 	/*
 	 * We set bucket width equal to num_mcelem / 0.007 as per the comment
@@ -575,7 +575,7 @@ compute_array_stats(VacAttrStats *stats, AnalyzeAttrFetchFunc fetchfunc,
 		count_items_count = hash_get_num_entries(count_tab);
 		if (count_items_count > 0)
 		{
-			int			num_hist = stats->attr->attstattarget;
+			int			num_hist = stats->attstattarget;
 			DECountItem **sorted_count_items;
 			int			j;
 			int			delta;

src/backend/utils/adt/rangetypes_typanalyze.c

@@ -47,18 +47,17 @@ range_typanalyze(PG_FUNCTION_ARGS)
 {
 	VacAttrStats *stats = (VacAttrStats *) PG_GETARG_POINTER(0);
 	TypeCacheEntry *typcache;
-	Form_pg_attribute attr = stats->attr;
 
 	/* Get information about range type; note column might be a domain */
 	typcache = range_get_typcache(fcinfo, getBaseType(stats->attrtypid));
 
-	if (attr->attstattarget < 0)
-		attr->attstattarget = default_statistics_target;
+	if (stats->attstattarget < 0)
+		stats->attstattarget = default_statistics_target;
 
 	stats->compute_stats = compute_range_stats;
 	stats->extra_data = typcache;
 	/* same as in std_typanalyze */
-	stats->minrows = 300 * attr->attstattarget;
+	stats->minrows = 300 * stats->attstattarget;
 
 	PG_RETURN_BOOL(true);
 }
@@ -74,18 +73,17 @@ multirange_typanalyze(PG_FUNCTION_ARGS)
 {
 	VacAttrStats *stats = (VacAttrStats *) PG_GETARG_POINTER(0);
 	TypeCacheEntry *typcache;
-	Form_pg_attribute attr = stats->attr;
 
 	/* Get information about multirange type; note column might be a domain */
 	typcache = multirange_get_typcache(fcinfo, getBaseType(stats->attrtypid));
 
-	if (attr->attstattarget < 0)
-		attr->attstattarget = default_statistics_target;
+	if (stats->attstattarget < 0)
+		stats->attstattarget = default_statistics_target;
 
 	stats->compute_stats = compute_range_stats;
 	stats->extra_data = typcache;
 	/* same as in std_typanalyze */
-	stats->minrows = 300 * attr->attstattarget;
+	stats->minrows = 300 * stats->attstattarget;
 
 	PG_RETURN_BOOL(true);
 }
@@ -136,7 +134,7 @@ compute_range_stats(VacAttrStats *stats, AnalyzeAttrFetchFunc fetchfunc,
 	int			empty_cnt = 0;
 	int			range_no;
 	int			slot_idx;
-	int			num_bins = stats->attr->attstattarget;
+	int			num_bins = stats->attstattarget;
 	int			num_hist;
 	float8	   *lengths;
 	RangeBound *lowers,

src/include/commands/vacuum.h

@@ -116,16 +116,12 @@ typedef struct VacAttrStats
 {
 	/*
 	 * These fields are set up by the main ANALYZE code before invoking the
-	 * type-specific typanalyze function.
-	 *
-	 * Note: do not assume that the data being analyzed has the same datatype
-	 * shown in attr, ie do not trust attr->atttypid, attlen, etc.  This is
-	 * because some index opclasses store a different type than the underlying
-	 * column/expression.  Instead use attrtypid, attrtypmod, and attrtype for
+	 * type-specific typanalyze function.  They don't necessarily match what
+	 * is in pg_attribute, because some index opclasses store a different type
+	 * than the underlying column/expression.  Therefore, use these fields for
 	 * information about the datatype being fed to the typanalyze function.
-	 * Likewise, use attrcollid not attr->attcollation.
 	 */
-	Form_pg_attribute attr;		/* copy of pg_attribute row for column */
+	int			attstattarget;
 	Oid			attrtypid;		/* type of data being analyzed */
 	int32		attrtypmod;		/* typmod of data being analyzed */
 	Form_pg_type attrtype;		/* copy of pg_type row for attrtypid */