ORCA ignores empty or unsupported ext stats

STATS_EXT_DEPENDENCIES can be empty after analyzed. This is
because when the degree of all combinations is 0, PG will
not record the dependencies data in pg_statistic_ext_data.

The current changes ensure that ORCA will not fail to
generate a plan due to failure to read dependencies data,
and also ignore unsupported ext stats type(STATS_EXT_EXPRESSIONS).

Author: jiaqizho

src/backend/gpopt/gpdbwrappers.cpp

@@ -1929,7 +1929,7 @@ gpdb::GetMVDependencies(Oid stat_oid)
 {
 	GP_WRAP_START;
 	{
-		return statext_dependencies_load(stat_oid);
+		return statext_dependencies_load(stat_oid, true);
 	}
 	GP_WRAP_END;
 }

src/backend/gpopt/translate/CTranslatorRelcacheToDXL.cpp

@@ -345,21 +345,24 @@ CTranslatorRelcacheToDXL::RetrieveExtStats(CMemoryPool *mp, IMDId *mdid)
 	if (list_member_int(kinds, STATS_EXT_DEPENDENCIES))
 	{
 		MVDependencies *dependencies = gpdb::GetMVDependencies(stat_oid);
+		// dependencies can be null after analyzed.
+		if (dependencies) {
 
-		for (ULONG i = 0; i < dependencies->ndeps; i++)
-		{
-			MVDependency *dep = dependencies->deps[i];
-
-			// Note: MVDependency->attributes's last index is the dependent "to"
-			//       column.
-			IntPtrArray *from_attnos = GPOS_NEW(mp) IntPtrArray(mp);
-			for (INT j = 0; j < dep->nattributes - 1; j++)
+			for (ULONG i = 0; i < dependencies->ndeps; i++)
 			{
-				from_attnos->Append(GPOS_NEW(mp) INT(dep->attributes[j]));
+				MVDependency *dep = dependencies->deps[i];
+
+				// Note: MVDependency->attributes's last index is the dependent "to"
+				//       column.
+				IntPtrArray *from_attnos = GPOS_NEW(mp) IntPtrArray(mp);
+				for (INT j = 0; j < dep->nattributes - 1; j++)
+				{
+					from_attnos->Append(GPOS_NEW(mp) INT(dep->attributes[j]));
+				}
+				deps->Append(GPOS_NEW(mp) CMDDependency(
+					mp, dep->degree, from_attnos,
+					dep->attributes[dep->nattributes - 1]));
 			}
-			deps->Append(GPOS_NEW(mp) CMDDependency(
-				mp, dep->degree, from_attnos,
-				dep->attributes[dep->nattributes - 1]));
 		}
 	}
 
@@ -442,12 +445,22 @@ CTranslatorRelcacheToDXL::RetrieveExtStatsInfo(CMemoryPool *mp, IMDId *mdid)
 				statkind = CMDExtStatsInfo::EstatMCV;
 				break;
 			}
+			case STATS_EXT_EXPRESSIONS:
+			{
+				statkind = CMDExtStatsInfo::EstatExpr;
+				break;
+			}
 			default:
 			{
 				GPOS_ASSERT(false && "Unknown extended stat type");
 			}
 		}
 
+		// CBDB_MERGE_FIXME: support expr ext stats in the feature
+		if (statkind == CMDExtStatsInfo::EstatExpr) {
+			continue;
+		}
+
 		const CWStringConst *statname = GPOS_NEW(mp)
 			CWStringConst(CDXLUtils::CreateDynamicStringFromCharArray(
 							  mp, gpdb::GetExtStatsName(info->statOid))

src/backend/gporca/libnaucrates/include/naucrates/md/CMDExtStatsInfo.h

@@ -42,6 +42,7 @@ class CMDExtStatsInfo : public CRefCount
 		EstatDependencies,
 		EstatNDistinct,
 		EstatMCV,
+		EstatExpr,
 		EstatSentinel
 	};
 

src/backend/statistics/dependencies.c

@@ -619,7 +619,7 @@ dependency_is_fully_matched(MVDependency *dependency, Bitmapset *attnums)
  *		Load the functional dependencies for the indicated pg_statistic_ext tuple
  */
 MVDependencies *
-statext_dependencies_load(Oid mvoid)
+statext_dependencies_load(Oid mvoid, bool allow_null)
 {
 	MVDependencies *result;
 	bool		isnull;
@@ -633,9 +633,17 @@ statext_dependencies_load(Oid mvoid)
 	deps = SysCacheGetAttr(STATEXTDATASTXOID, htup,
 						   Anum_pg_statistic_ext_data_stxddependencies, &isnull);
 	if (isnull)
-		elog(ERROR,
-			 "requested statistics kind \"%c\" is not yet built for statistics object %u",
-			 STATS_EXT_DEPENDENCIES, mvoid);
+	{
+		if (!allow_null)
+		{
+			elog(ERROR,
+				"requested statistics kind \"%c\" is not yet built for statistics object %u",
+				STATS_EXT_DEPENDENCIES, mvoid);
+		}
+
+		ReleaseSysCache(htup);
+		return NULL;
+	}
 
 	result = statext_dependencies_deserialize(DatumGetByteaPP(deps));
 
@@ -1656,7 +1664,7 @@ dependencies_clauselist_selectivity(PlannerInfo *root,
 		if (nmatched + nexprs < 2)
 			continue;
 
-		deps = statext_dependencies_load(stat->statOid);
+		deps = statext_dependencies_load(stat->statOid, false);
 
 		/*
 		 * The expressions may be represented by different attnums in the

src/include/statistics/statistics.h

@@ -95,7 +95,7 @@ typedef struct MCVList
 } MCVList;
 
 extern MVNDistinct *statext_ndistinct_load(Oid mvoid);
-extern MVDependencies *statext_dependencies_load(Oid mvoid);
+extern MVDependencies *statext_dependencies_load(Oid mvoid, bool allow_null);
 extern MCVList *statext_mcv_load(Oid mvoid);
 
 extern void BuildRelationExtStatistics(Relation onerel, double totalrows,