Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL)

The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates
cloning of extended statistics on the source table, but it failed to do
so.  Patch it up so that it does.  Also include an INCLUDING STATISTICS
option to the LIKE clause, so that the behavior can be requested
individually, or excluded individually.

While at it, reorder the INCLUDING options, both in code and in docs, in
alphabetical order which makes more sense than feature-implementation
order that was previously used.

Backpatch this to Postgres 10, where extended statistics were
introduced, because this is seen as an oversight in a fresh feature
which is better to get consistent from the get-go instead of changing
only in pg11.

In pg11, comments on statistics objects are cloned too.  In pg10 they
are not, because I (Álvaro) was too coward to change the parse node as
required to support it.  Also, in pg10 I chose not to renumber the
parser symbols for the various INCLUDING options in LIKE, for the same
reason.  Any corresponding user-visible changes (docs) are backpatched,
though.

Reported-by: Stephen Froehlich
Author: David Rowley
Reviewed-by: Álvaro Herrera, Tomas Vondra
Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com

1 files changed, 143 insertions, 0 deletions

diff --git a/src/backend/parser/parse_utilcmd.c b/src/backend/parser/parse_utilcmd.c
index 6029eb13d7f..8c7bd686397 100644
--- a/src/backend/parser/parse_utilcmd.c
+++ b/src/backend/parser/parse_utilcmd.c
@@ -39,6 +39,7 @@
 #include "catalog/pg_constraint_fn.h"
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_operator.h"
+#include "catalog/pg_statistic_ext.h"
 #include "catalog/pg_type.h"
 #include "commands/comment.h"
 #include "commands/defrem.h"
@@ -85,6 +86,7 @@ typedef struct
 	List	   *fkconstraints;	/* FOREIGN KEY constraints */
 	List	   *ixconstraints;	/* index-creating constraints */
 	List	   *inh_indexes;	/* cloned indexes from INCLUDING INDEXES */
+	List	   *extstats;		/* cloned extended statistics */
 	List	   *blist;			/* "before list" of things to do before
 								 * creating the table */
 	List	   *alist;			/* "after list" of things to do after creating
@@ -118,11 +120,14 @@ static void transformTableLikeClause(CreateStmtContext *cxt,
 						 TableLikeClause *table_like_clause);
 static void transformOfType(CreateStmtContext *cxt,
 				TypeName *ofTypename);
+static CreateStatsStmt *generateClonedExtStatsStmt(RangeVar *heapRel,
+						   Oid heapRelid, Oid source_statsid);
 static List *get_collation(Oid collation, Oid actual_datatype);
 static List *get_opclass(Oid opclass, Oid actual_datatype);
 static void transformIndexConstraints(CreateStmtContext *cxt);
 static IndexStmt *transformIndexConstraint(Constraint *constraint,
 						 CreateStmtContext *cxt);
+static void transformExtendedStatistics(CreateStmtContext *cxt);
 static void transformFKConstraints(CreateStmtContext *cxt,
 					   bool skipValidation,
 					   bool isAddConstraint);
@@ -234,6 +239,7 @@ transformCreateStmt(CreateStmt *stmt, const char *queryString)
 	cxt.fkconstraints = NIL;
 	cxt.ixconstraints = NIL;
 	cxt.inh_indexes = NIL;
+	cxt.extstats = NIL;
 	cxt.blist = NIL;
 	cxt.alist = NIL;
 	cxt.pkey = NULL;
@@ -335,6 +341,11 @@ transformCreateStmt(CreateStmt *stmt, const char *queryString)
 	transformCheckConstraints(&cxt, !is_foreign_table ? true : false);
 
 	/*
+	 * Postprocess extended statistics.
+	 */
+	transformExtendedStatistics(&cxt);
+
+	/*
 	 * Output results.
 	 */
 	stmt->tableElts = cxt.columns;
@@ -1190,6 +1201,43 @@ transformTableLikeClause(CreateStmtContext *cxt, TableLikeClause *table_like_cla
 	}
 
 	/*
+	 * Likewise, copy extended statistics if requested
+	 */
+	if (table_like_clause->options & CREATE_TABLE_LIKE_STATISTICS)
+	{
+		List		   *parent_extstats;
+		ListCell	   *l;
+
+		parent_extstats = RelationGetStatExtList(relation);
+
+		foreach(l, parent_extstats)
+		{
+			Oid		parent_stat_oid = lfirst_oid(l);
+			CreateStatsStmt *stats_stmt;
+
+			stats_stmt = generateClonedExtStatsStmt(cxt->relation,
+													RelationGetRelid(relation),
+													parent_stat_oid);
+
+			/* Copy comment on statistics object, if requested */
+			if (table_like_clause->options & CREATE_TABLE_LIKE_COMMENTS)
+			{
+				comment = GetComment(parent_stat_oid, StatisticExtRelationId, 0);
+
+				/*
+				 * We make use of CreateStatsStmt's stxcomment option, so as
+				 * not to need to know now what name the statistics will have.
+				 */
+				stats_stmt->stxcomment = comment;
+			}
+
+			cxt->extstats = lappend(cxt->extstats, stats_stmt);
+		}
+
+		list_free(parent_extstats);
+	}
+
+	/*
 	 * Close the parent rel, but keep our AccessShareLock on it until xact
 	 * commit.  That will prevent someone else from deleting or ALTERing the
 	 * parent before the child is committed.
@@ -1567,6 +1615,85 @@ generateClonedIndexStmt(RangeVar *heapRel, Oid heapRelid, Relation source_idx,
 }
 
 /*
+ * Generate a CreateStatsStmt node using information from an already existing
+ * extended statistic "source_statsid", for the rel identified by heapRel and
+ * heapRelid.
+ */
+static CreateStatsStmt *
+generateClonedExtStatsStmt(RangeVar *heapRel, Oid heapRelid,
+						   Oid source_statsid)
+{
+	HeapTuple		ht_stats;
+	Form_pg_statistic_ext statsrec;
+	CreateStatsStmt *stats;
+	List		   *stat_types = NIL;
+	List		   *def_names = NIL;
+	bool			 isnull;
+	Datum			datum;
+	ArrayType	   *arr;
+	char		   *enabled;
+	int				i;
+
+	Assert(OidIsValid(heapRelid));
+	Assert(heapRel != NULL);
+
+	/*
+	 * Fetch pg_statistic_ext tuple of source statistics object.
+	 */
+	ht_stats = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(source_statsid));
+	if (!HeapTupleIsValid(ht_stats))
+		elog(ERROR, "cache lookup failed for statistics object %u", source_statsid);
+	statsrec = (Form_pg_statistic_ext) GETSTRUCT(ht_stats);
+
+	/* Determine which statistics types exist */
+	datum = SysCacheGetAttr(STATEXTOID, ht_stats,
+							Anum_pg_statistic_ext_stxkind, &isnull);
+	Assert(!isnull);
+	arr = DatumGetArrayTypeP(datum);
+	if (ARR_NDIM(arr) != 1 ||
+		ARR_HASNULL(arr) ||
+		ARR_ELEMTYPE(arr) != CHAROID)
+		elog(ERROR, "stxkind is not a 1-D char array");
+	enabled = (char *) ARR_DATA_PTR(arr);
+	for (i = 0; i < ARR_DIMS(arr)[0]; i++)
+	{
+		if (enabled[i] == STATS_EXT_NDISTINCT)
+			stat_types = lappend(stat_types, makeString("ndistinct"));
+		else if (enabled[i] == STATS_EXT_DEPENDENCIES)
+			stat_types = lappend(stat_types, makeString("dependencies"));
+		else
+			elog(ERROR, "unrecognized statistics kind %c", enabled[i]);
+	}
+
+	/* Determine which columns the statistics are on */
+	for (i = 0; i < statsrec->stxkeys.dim1; i++)
+	{
+		ColumnRef  *cref = makeNode(ColumnRef);
+		AttrNumber	attnum = statsrec->stxkeys.values[i];
+
+		cref->fields = list_make1(makeString(get_attname(heapRelid,
+														 attnum, false)));
+		cref->location = -1;
+
+		def_names = lappend(def_names, cref);
+	}
+
+	/* finally, build the output node */
+	stats = makeNode(CreateStatsStmt);
+	stats->defnames = NULL;
+	stats->stat_types = stat_types;
+	stats->exprs = def_names;
+	stats->relations = list_make1(heapRel);
+	stats->stxcomment = NULL;
+	stats->if_not_exists = false;
+
+	/* Clean up */
+	ReleaseSysCache(ht_stats);
+
+	return stats;
+}
+
+/*
  * get_collation		- fetch qualified name of a collation
  *
  * If collation is InvalidOid or is the default for the given actual_datatype,
@@ -2120,6 +2247,18 @@ transformIndexConstraint(Constraint *constraint, CreateStmtContext *cxt)
 }
 
 /*
+ * transformExtendedStatistics
+ *     Handle extended statistic objects
+ *
+ * Right now, there's nothing to do here, so we just copy the list.
+ */
+static void
+transformExtendedStatistics(CreateStmtContext *cxt)
+{
+	cxt->alist = list_concat(cxt->alist, cxt->extstats);
+}
+
+/*
  * transformCheckConstraints
  *		handle CHECK constraints
  *
@@ -2695,6 +2834,7 @@ transformAlterTableStmt(Oid relid, AlterTableStmt *stmt,
 	cxt.fkconstraints = NIL;
 	cxt.ixconstraints = NIL;
 	cxt.inh_indexes = NIL;
+	cxt.extstats = NIL;
 	cxt.blist = NIL;
 	cxt.alist = NIL;
 	cxt.pkey = NULL;
@@ -2957,6 +3097,9 @@ transformAlterTableStmt(Oid relid, AlterTableStmt *stmt,
 		newcmds = lappend(newcmds, newcmd);
 	}
 
+	/* Append extended statistic objects */
+	transformExtendedStatistics(&cxt);
+
 	/* Close rel */
 	relation_close(rel, NoLock);