diff --git a/createas.c b/createas.c
index a26bad1..21ca067 100644
--- a/createas.c
+++ b/createas.c
@@ -11,6 +11,7 @@
  */
 #include "postgres.h"
 
+#include "access/xact.h"
 #include "access/genam.h"
 #include "access/heapam.h"
 #include "catalog/dependency.h"
@@ -70,6 +71,10 @@ static Bitmapset *get_primary_key_attnos_from_query(Query *query, List **constra
 
 static void StoreImmvQuery(Oid viewOid, Query *viewQuery);
 
+#if defined(PG_VERSION_NUM) && (PG_VERSION_NUM < 140000)
+static bool CreateTableAsRelExists(CreateTableAsStmt *ctas);
+#endif
+
 /*
  * ExecCreateImmv -- execute a create_immv() function
  *
@@ -286,7 +291,11 @@ rewriteQueryForIMMV(Query *query, List *colNames)
 	{
 		rewritten->groupClause = transformDistinctClause(NULL, &rewritten->targetList, rewritten->sortClause, false);
 
+#if defined(PG_VERSION_NUM) && (PG_VERSION_NUM >= 140000)
 		fn = makeFuncCall(list_make1(makeString("count")), NIL, COERCE_EXPLICIT_CALL, -1);
+#else
+		fn = makeFuncCall(list_make1(makeString("count")), NIL, -1);
+#endif
 		fn->agg_star = true;
 
 		node = ParseFuncOrColumn(pstate, fn->funcname, NIL, NULL, fn, false, -1);
@@ -869,8 +878,9 @@ get_primary_key_attnos_from_query(Query *query, List **constraintList, bool is_c
 	int i;
 	Bitmapset *keys = NULL;
 	Relids	rels_in_from;
+#if defined(PG_VERSION_NUM) && (PG_VERSION_NUM >= 140000)
 	PlannerInfo root;
-
+#endif
 
 	/*
 	 * Collect primary key attributes from all tables used in query. The key attributes
@@ -939,8 +949,11 @@ get_primary_key_attnos_from_query(Query *query, List **constraintList, bool is_c
 	}
 
 	/* Collect relations appearing in the FROM clause */
+#if defined(PG_VERSION_NUM) && (PG_VERSION_NUM >= 140000)
 	rels_in_from = pull_varnos_of_level(&root, (Node *)query->jointree, 0);
-
+#else
+	rels_in_from = pull_varnos_of_level((Node *)query->jointree, 0);
+#endif
 	/*
 	 * Check if all key attributes of relations in FROM are appearing in the target
 	 * list.  If an attribute remains in key_attnos_list in spite of the table is used
@@ -997,3 +1010,39 @@ StoreImmvQuery(Oid viewOid, Query *viewQuery)
 	CommandCounterIncrement();
 }
 
+#if defined(PG_VERSION_NUM) && (PG_VERSION_NUM < 140000)
+/*
+ * CreateTableAsRelExists --- check existence of relation for CreateTableAsStmt
+ *
+ * Utility wrapper checking if the relation pending for creation in this
+ * CreateTableAsStmt query already exists or not.  Returns true if the
+ * relation exists, otherwise false.
+ */
+static bool
+CreateTableAsRelExists(CreateTableAsStmt *ctas)
+{
+	Oid			nspid;
+	IntoClause *into = ctas->into;
+
+	nspid = RangeVarGetCreationNamespace(into->rel);
+
+	if (get_relname_relid(into->rel->relname, nspid))
+	{
+		if (!ctas->if_not_exists)
+			ereport(ERROR,
+					(errcode(ERRCODE_DUPLICATE_TABLE),
+					 errmsg("relation \"%s\" already exists",
+							into->rel->relname)));
+
+		/* The relation exists and IF NOT EXISTS has been specified */
+		ereport(NOTICE,
+				(errcode(ERRCODE_DUPLICATE_TABLE),
+				 errmsg("relation \"%s\" already exists, skipping",
+						into->rel->relname)));
+		return true;
+	}
+
+	/* Relation does not exist, it can be created */
+	return false;
+}
+#endif
diff --git a/matview.c b/matview.c
index 9905ec2..cf6f4c3 100644
--- a/matview.c
+++ b/matview.c
@@ -25,6 +25,7 @@
 #include "parser/parse_clause.h"
 #include "parser/parse_func.h"
 #include "parser/parse_relation.h"
+#include "parser/parser.h"
 #include "rewrite/rewriteHandler.h"
 #include "rewrite/rowsecurity.h"
 #include "storage/lmgr.h"
@@ -566,13 +567,19 @@ IVM_immediate_maintenance(PG_FUNCTION_ARGS)
 
 		old_tuplestore = tuplestore_begin_heap(false, false, work_mem);
 		dest_old = CreateDestReceiver(DestTuplestore);
+#if defined(PG_VERSION_NUM) && (PG_VERSION_NUM >= 140000)
 		SetTuplestoreDestReceiverParams(dest_old,
 									old_tuplestore,
 									TopTransactionContext,
 									false,
 									NULL,
 									NULL);
-
+#else
+		SetTuplestoreDestReceiverParams(dest_old,
+									old_tuplestore,
+									TopTransactionContext,
+									false);
+#endif
 		MemoryContextSwitchTo(oldcxt);
 	}
 	if (entry->has_new)
@@ -581,12 +588,19 @@ IVM_immediate_maintenance(PG_FUNCTION_ARGS)
 
 		new_tuplestore = tuplestore_begin_heap(false, false, work_mem);
 		dest_new = CreateDestReceiver(DestTuplestore);
+#if defined(PG_VERSION_NUM) && (PG_VERSION_NUM >= 140000)
 		SetTuplestoreDestReceiverParams(dest_new,
 									new_tuplestore,
 									TopTransactionContext,
 									false,
 									NULL,
 									NULL);
+#else
+		SetTuplestoreDestReceiverParams(dest_new,
+									new_tuplestore,
+									TopTransactionContext,
+									false);
+#endif
 		MemoryContextSwitchTo(oldcxt);
 	}
 
@@ -843,7 +857,12 @@ get_prestate_rte(RangeTblEntry *rte, MV_TriggerTable *table,
 			make_delta_enr_name("old", table->table_id, i));
 	}
 
+
+#if defined(PG_VERSION_NUM) && (PG_VERSION_NUM >= 140000)
 	raw = (RawStmt*)linitial(raw_parser(str.data, RAW_PARSE_DEFAULT));
+#else
+	raw = (RawStmt*)linitial(raw_parser(str.data));
+#endif
 	sub = transformStmt(pstate, raw->stmt);
 
 	/* If this query has setOperations, RTEs in rtables has a subquery which contains ENR */
@@ -942,7 +961,11 @@ union_ENRs(RangeTblEntry *rte, Oid relid, List *enr_rtes, const char *prefix,
 			make_delta_enr_name(prefix, relid, i));
 	}
 
+#if defined(PG_VERSION_NUM) && (PG_VERSION_NUM >= 140000)
 	raw = (RawStmt*)linitial(raw_parser(str.data, RAW_PARSE_DEFAULT));
+#else
+	raw = (RawStmt*)linitial(raw_parser(str.data));
+#endif
 	sub = transformStmt(pstate, raw->stmt);
 
 	rte->rtekind = RTE_SUBQUERY;
@@ -982,7 +1005,11 @@ rewrite_query_for_distinct(Query *query, ParseState *pstate)
 	Node *node;
 
 	/* Add count(*) for counting distinct tuples in views */
+#if defined(PG_VERSION_NUM) && (PG_VERSION_NUM >= 140000)
 	fn = makeFuncCall(list_make1(makeString("count")), NIL, COERCE_EXPLICIT_CALL, -1);
+#else
+	fn = makeFuncCall(list_make1(makeString("count")), NIL, -1);
+#endif
 	fn->agg_star = true;
 	if (!query->groupClause && !query->hasAggs)
 		query->groupClause = transformDistinctClause(NULL, &query->targetList, query->sortClause, false);
diff --git a/pg_ivm.c b/pg_ivm.c
index 638c9de..ae00655 100644
--- a/pg_ivm.c
+++ b/pg_ivm.c
@@ -185,7 +185,11 @@ create_immv(PG_FUNCTION_ARGS)
 
 	ctas = makeNode(CreateTableAsStmt);
 	ctas->query = parsetree->stmt;
+#if defined(PG_VERSION_NUM) && (PG_VERSION_NUM >= 140000)
 	ctas->objtype = OBJECT_MATVIEW;
+#else
+	ctas->relkind = OBJECT_MATVIEW;
+#endif
 	ctas->is_select_into = false;
 	ctas->into = makeNode(IntoClause);
 	ctas->into->rel = makeRangeVarFromNameList(names);