1 files changed, 142 insertions, 27 deletions

diff --git a/src/backend/commands/statscmds.c b/src/backend/commands/statscmds.c
index e90a14273b7..f46ef01134f 100644
--- a/src/backend/commands/statscmds.c
+++ b/src/backend/commands/statscmds.c
@@ -20,6 +20,7 @@
 #include "catalog/namespace.h"
 #include "catalog/pg_namespace.h"
 #include "catalog/pg_statistic_ext.h"
+#include "commands/comment.h"
 #include "commands/defrem.h"
 #include "miscadmin.h"
 #include "statistics/statistics.h"
@@ -31,6 +32,11 @@
 #include "utils/typcache.h"
 
 
+static char *ChooseExtendedStatisticName(const char *name1, const char *name2,
+							const char *label, Oid namespaceid);
+static char *ChooseExtendedStatisticNameAddition(List *exprs);
+
+
 /* qsort comparator for the attnums in CreateStatistics */
 static int
 compare_int16(const void *a, const void *b)
@@ -51,7 +57,6 @@ CreateStatistics(CreateStatsStmt *stmt)
 	int16		attnums[STATS_MAX_DIMENSIONS];
 	int			numcols = 0;
 	char	   *namestr;
-	NameData	stxname;
 	Oid			statoid;
 	Oid			namespaceId;
 	Oid			stxowner = GetUserId();
@@ -75,31 +80,6 @@ CreateStatistics(CreateStatsStmt *stmt)
 
 	Assert(IsA(stmt, CreateStatsStmt));
 
-	/* resolve the pieces of the name (namespace etc.) */
-	namespaceId = QualifiedNameGetCreationNamespace(stmt->defnames, &namestr);
-	namestrcpy(&stxname, namestr);
-
-	/*
-	 * Deal with the possibility that the statistics object already exists.
-	 */
-	if (SearchSysCacheExists2(STATEXTNAMENSP,
-							  NameGetDatum(&stxname),
-							  ObjectIdGetDatum(namespaceId)))
-	{
-		if (stmt->if_not_exists)
-		{
-			ereport(NOTICE,
-					(errcode(ERRCODE_DUPLICATE_OBJECT),
-					 errmsg("statistics object \"%s\" already exists, skipping",
-							namestr)));
-			return InvalidObjectAddress;
-		}
-
-		ereport(ERROR,
-				(errcode(ERRCODE_DUPLICATE_OBJECT),
-				 errmsg("statistics object \"%s\" already exists", namestr)));
-	}
-
 	/*
 	 * Examine the FROM clause.  Currently, we only allow it to be a single
 	 * simple table, but later we'll probably allow multiple tables and JOIN
@@ -149,6 +129,45 @@ CreateStatistics(CreateStatsStmt *stmt)
 	relid = RelationGetRelid(rel);
 
 	/*
+	 * If the node has a name, split it up and determine creation namespace.
+	 * If not (a possibility not considered by the grammar, but one which can
+	 * occur via the "CREATE TABLE ... (LIKE)" command), then we put the
+	 * object in the same namespace as the relation, and cons up a name for it.
+	 */
+	if (stmt->defnames)
+		namespaceId = QualifiedNameGetCreationNamespace(stmt->defnames, &namestr);
+	else
+	{
+		namespaceId = RelationGetNamespace(rel);
+		namestr = ChooseExtendedStatisticName(RelationGetRelationName(rel),
+											  ChooseExtendedStatisticNameAddition(stmt->exprs),
+											  "stat",
+											  namespaceId);
+	}
+
+	/*
+	 * Deal with the possibility that the statistics object already exists.
+	 */
+	if (SearchSysCacheExists2(STATEXTNAMENSP,
+							  CStringGetDatum(namestr),
+							  ObjectIdGetDatum(namespaceId)))
+	{
+		if (stmt->if_not_exists)
+		{
+			ereport(NOTICE,
+					(errcode(ERRCODE_DUPLICATE_OBJECT),
+					 errmsg("statistics object \"%s\" already exists, skipping",
+							namestr)));
+			relation_close(rel, NoLock);
+			return InvalidObjectAddress;
+		}
+
+		ereport(ERROR,
+				(errcode(ERRCODE_DUPLICATE_OBJECT),
+				 errmsg("statistics object \"%s\" already exists", namestr)));
+	}
+
+	/*
 	 * Currently, we only allow simple column references in the expression
 	 * list.  That will change someday, and again the grammar already supports
 	 * it so we have to enforce restrictions here.  For now, we can convert
@@ -288,7 +307,7 @@ CreateStatistics(CreateStatsStmt *stmt)
 	memset(values, 0, sizeof(values));
 	memset(nulls, false, sizeof(nulls));
 	values[Anum_pg_statistic_ext_stxrelid - 1] = ObjectIdGetDatum(relid);
-	values[Anum_pg_statistic_ext_stxname - 1] = NameGetDatum(&stxname);
+	values[Anum_pg_statistic_ext_stxname - 1] = CStringGetDatum(namestr);
 	values[Anum_pg_statistic_ext_stxnamespace - 1] = ObjectIdGetDatum(namespaceId);
 	values[Anum_pg_statistic_ext_stxowner - 1] = ObjectIdGetDatum(stxowner);
 	values[Anum_pg_statistic_ext_stxkeys - 1] = PointerGetDatum(stxkeys);
@@ -340,6 +359,11 @@ CreateStatistics(CreateStatsStmt *stmt)
 	 * STATISTICS, which is more work than it seems worth.
 	 */
 
+	/* Add any requested comment */
+	if (stmt->stxcomment != NULL)
+		CreateComments(statoid, StatisticExtRelationId, 0,
+					   stmt->stxcomment);
+
 	/* Return stats object's address */
 	return myself;
 }
@@ -405,3 +429,94 @@ UpdateStatisticsForTypeChange(Oid statsOid, Oid relationOid, int attnum,
 	 * Future types of extended stats will likely require us to work harder.
 	 */
 }
+
+/*
+ * Select a nonconflicting name for a new statistics.
+ *
+ * name1, name2, and label are used the same way as for makeObjectName(),
+ * except that the label can't be NULL; digits will be appended to the label
+ * if needed to create a name that is unique within the specified namespace.
+ *
+ * Returns a palloc'd string.
+ *
+ * Note: it is theoretically possible to get a collision anyway, if someone
+ * else chooses the same name concurrently.  This is fairly unlikely to be
+ * a problem in practice, especially if one is holding a share update
+ * exclusive lock on the relation identified by name1.  However, if choosing
+ * multiple names within a single command, you'd better create the new object
+ * and do CommandCounterIncrement before choosing the next one!
+ */
+static char *
+ChooseExtendedStatisticName(const char *name1, const char *name2,
+							const char *label, Oid namespaceid)
+{
+	int			pass = 0;
+	char	   *stxname = NULL;
+	char		modlabel[NAMEDATALEN];
+
+	/* try the unmodified label first */
+	StrNCpy(modlabel, label, sizeof(modlabel));
+
+	for (;;)
+	{
+		Oid		existingstats;
+
+		stxname = makeObjectName(name1, name2, modlabel);
+
+		existingstats = GetSysCacheOid2(STATEXTNAMENSP,
+										PointerGetDatum(stxname),
+										ObjectIdGetDatum(namespaceid));
+		if (!OidIsValid(existingstats))
+			break;
+
+		/* found a conflict, so try a new name component */
+		pfree(stxname);
+		snprintf(modlabel, sizeof(modlabel), "%s%d", label, ++pass);
+	}
+
+	return stxname;
+}
+
+/*
+ * Generate "name2" for a new statistics given the list of column names for it
+ * This will be passed to ChooseExtendedStatisticName along with the parent
+ * table name and a suitable label.
+ *
+ * We know that less than NAMEDATALEN characters will actually be used,
+ * so we can truncate the result once we've generated that many.
+ *
+ * XXX see also ChooseIndexNameAddition.
+ */
+static char *
+ChooseExtendedStatisticNameAddition(List *exprs)
+{
+	char		buf[NAMEDATALEN * 2];
+	int			buflen = 0;
+	ListCell   *lc;
+
+	buf[0] = '\0';
+	foreach(lc, exprs)
+	{
+		ColumnRef *cref = (ColumnRef *) lfirst(lc);
+		const char *name;
+
+		/* It should be one of these, but just skip if it happens not to be */
+		if (!IsA(cref, ColumnRef))
+			continue;
+
+		name = strVal((Value *) linitial(cref->fields));
+
+		if (buflen > 0)
+			buf[buflen++] = '_';	/* insert _ between names */
+
+		/*
+		 * At this point we have buflen <= NAMEDATALEN.  name should be less
+		 * than NAMEDATALEN already, but use strlcpy for paranoia.
+		 */
+		strlcpy(buf + buflen, name, NAMEDATALEN);
+		buflen += strlen(buf + buflen);
+		if (buflen >= NAMEDATALEN)
+			break;
+	}
+	return pstrdup(buf);
+}