Handle exceptions caused by partitioned tables (#412)

We don't support reading from partitioned tables yet and 
as reported in #409 this can cause crashes. So for now
disallow DuckDB execution when partitioned tables are
involved in the query. 

Supporting partitioned tables is tracked in #19

src/pgduckdb_hooks.cpp

@@ -52,6 +52,23 @@ IsCatalogTable(List *tables) {
 	return false;
 }
 
+static bool
+ContainsPartitionedTable(List *rtes) {
+	foreach_node(RangeTblEntry, rte, rtes) {
+		if (rte->rtekind == RTE_SUBQUERY) {
+			/* Check whether any table in the subquery is a partitioned table */
+			if (ContainsPartitionedTable(rte->subquery->rtable)) {
+				return true;
+			}
+		}
+
+		if (rte->relkind == RELKIND_PARTITIONED_TABLE) {
+			return true;
+		}
+	}
+	return false;
+}
+
 static bool
 IsDuckdbTable(Oid relid) {
 	if (relid == InvalidOid) {
@@ -147,6 +164,14 @@ IsAllowedStatement(Query *query, bool throw_error = false) {
 		return false;
 	}
 
+	/*
+	 * When accessing the partitioned table, we temporarily let PG handle it instead of DuckDB.
+	 */
+	if (ContainsPartitionedTable(query->rtable)) {
+		elog(elevel, "DuckDB does not support querying PG partitioned table");
+		return false;
+	}
+
 	/*
 	 * We don't support multi-statement transactions yet, so don't try to
 	 * execute queries in them even if duckdb.force_execution is enabled.

test/regression/expected/basic.out

@@ -72,3 +72,12 @@ SELECT COUNT(b) FROM t WHERE a > 3;
 (1 row)
 
 DROP TABLE t;
+CREATE TABLE t (a INT) PARTITION BY LIST (a);
+CREATE TABLE s (b INT);
+SELECT * FROM t JOIN s ON a = b;
+ a | b 
+---+---
+(0 rows)
+
+DROP TABLE t;
+DROP TABLE s;

test/regression/sql/basic.sql

@@ -47,3 +47,9 @@ INSERT INTO t SELECT g % 100, MD5(g::VARCHAR) FROM generate_series(1,1000) g;
 INSERT INTO t SELECT g % 100, MD5(g::VARCHAR) FROM generate_series(1,1000) g;
 SELECT COUNT(b) FROM t WHERE a > 3;
 DROP TABLE t;
+
+CREATE TABLE t (a INT) PARTITION BY LIST (a);
+CREATE TABLE s (b INT);
+SELECT * FROM t JOIN s ON a = b;
+DROP TABLE t;
+DROP TABLE s;