Allow writes to columnstore and Postgres tables in the same transaction

Remove the lockdowns introduced in duckdb/pg_duckdb#433 since the same restriction doesn't apply to us. In our case, Postgres remains the source of truth for columnstore tables, and DuckDB serves purely as the execution engine for reading and writing to those tables.

src/pgduckdb/pgduckdb_hooks.cpp

@@ -163,12 +163,12 @@ IsAllowedStatement(Query *query, bool throw_error = false) {
 			elog(elevel, "DuckDB does not support modififying Postgres tables");
 			return false;
 		}
-		if (pgduckdb::pg::IsInTransactionBlock(true)) {
-			if (pgduckdb::pg::DidWalWrites()) {
-				elog(elevel, "Writing to DuckDB and Postgres tables in the same transaction block is not supported");
-				return false;
-			}
-		}
+		// if (pgduckdb::pg::IsInTransactionBlock(true)) {
+		// 	if (pgduckdb::pg::DidWalWrites()) {
+		// 		elog(elevel, "Writing to DuckDB and Postgres tables in the same transaction block is not supported");
+		// 		return false;
+		// 	}
+		// }
 	}
 
 	/*
@@ -242,10 +242,10 @@ DuckdbPlannerHook_Cpp(Query *parse, const char *query_string, int cursor_options
 			}
 			/* If we can't create a plan, we'll fall back to Postgres */
 		}
-		if (parse->commandType != CMD_SELECT && pgduckdb::ddb::DidWrites() &&
-		    pgduckdb::pg::IsInTransactionBlock(true)) {
-			elog(ERROR, "Writing to DuckDB and Postgres tables in the same transaction block is not supported");
-		}
+		// if (parse->commandType != CMD_SELECT && pgduckdb::ddb::DidWrites() &&
+		//     pgduckdb::pg::IsInTransactionBlock(true)) {
+		// 	elog(ERROR, "Writing to DuckDB and Postgres tables in the same transaction block is not supported");
+		// }
 	}
 
 	/*

src/pgduckdb/pgduckdb_xact.cpp

@@ -41,7 +41,7 @@ PreventInTransactionBlock(const char *statement_type) {
  * IMPORTANT: This function should only be called at trasaction commit. At
  * other points in the transaction lifecycle its return value is not reliable.
  */
-static bool
+[[maybe_unused]] static bool
 DidWritesAtTransactionEnd() {
 	return pg::DidWalWrites() || pg::GetCurrentCommandId() > duckdb_command_id + 1;
 }
@@ -87,10 +87,10 @@ ClaimCurrentCommandId() {
 		return;
 	}
 
-	if (new_command_id != duckdb_command_id + 1) {
-		throw duckdb::NotImplementedException(
-		    "Writing to DuckDB and Postgres tables in the same transaction block is not supported");
-	}
+	// if (new_command_id != duckdb_command_id + 1) {
+	// 	throw duckdb::NotImplementedException(
+	// 	    "Writing to DuckDB and Postgres tables in the same transaction block is not supported");
+	// }
 
 	duckdb_command_id = new_command_id;
 }
@@ -157,12 +157,12 @@ DuckdbXactCallback_Cpp(XactEvent event) {
 	switch (event) {
 	case XACT_EVENT_PRE_COMMIT:
 	case XACT_EVENT_PARALLEL_PRE_COMMIT:
-		if (pg::IsInTransactionBlock(top_level_statement)) {
-			if (pg::DidWritesAtTransactionEnd() && ddb::DidWrites(context)) {
-				throw duckdb::NotImplementedException(
-				    "Writing to DuckDB and Postgres tables in the same transaction block is not supported");
-			}
-		}
+		// if (pg::IsInTransactionBlock(top_level_statement)) {
+		// 	if (pg::DidWritesAtTransactionEnd() && ddb::DidWrites(context)) {
+		// 		throw duckdb::NotImplementedException(
+		// 		    "Writing to DuckDB and Postgres tables in the same transaction block is not supported");
+		// 	}
+		// }
 		top_level_statement = true;
 		duckdb_command_id = -1;
 		// Commit the DuckDB transaction too

test/expected/transaction.out

@@ -0,0 +1,19 @@
+CREATE TABLE s (a int);
+CREATE TABLE t (b int) USING columnstore;
+BEGIN;
+INSERT INTO s VALUES (1);
+INSERT INTO t VALUES (2);
+COMMIT;
+SELECT * FROM s;
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM t;
+ b 
+---
+ 2
+(1 row)
+
+DROP TABLE s, t;

test/sql/transaction.sql

@@ -0,0 +1,12 @@
+CREATE TABLE s (a int);
+CREATE TABLE t (b int) USING columnstore;
+
+BEGIN;
+INSERT INTO s VALUES (1);
+INSERT INTO t VALUES (2);
+COMMIT;
+
+SELECT * FROM s;
+SELECT * FROM t;
+
+DROP TABLE s, t;