Start one background worker per database

include/pgduckdb/pgduckdb_guc.h

@@ -9,7 +9,6 @@ extern bool duckdb_allow_unsigned_extensions;
 extern bool duckdb_autoinstall_known_extensions;
 extern bool duckdb_autoload_known_extensions;
 extern int duckdb_max_workers_per_postgres_scan;
-extern char *duckdb_motherduck_postgres_database;
 extern int duckdb_motherduck_enabled;
 extern char *duckdb_motherduck_token;
 extern char *duckdb_postgres_role;

include/pgduckdb/pgduckdb_metadata_cache.hpp

@@ -10,7 +10,6 @@ Oid ExtensionOid();
 Oid DuckdbTableAmOid();
 bool IsMotherDuckEnabled();
 bool IsMotherDuckEnabledAnywhere();
-bool IsMotherDuckPostgresDatabase();
 Oid MotherDuckPostgresUser();
 Oid IsDuckdbTable(Form_pg_class relation);
 Oid IsDuckdbTable(Relation relation);

src/pgduckdb.cpp

@@ -18,7 +18,6 @@ bool duckdb_force_execution = false;
 int duckdb_max_workers_per_postgres_scan = 2;
 int duckdb_motherduck_enabled = MotherDuckEnabled::MOTHERDUCK_AUTO;
 char *duckdb_motherduck_token = strdup("");
-char *duckdb_motherduck_postgres_database = strdup("postgres");
 char *duckdb_motherduck_default_database = strdup("");
 char *duckdb_postgres_role = strdup("");
 
@@ -175,9 +174,6 @@ DuckdbInitGUC(void) {
 	DefineCustomVariable("duckdb.motherduck_token", "The token to use for MotherDuck", &duckdb_motherduck_token,
 	                     PGC_POSTMASTER, GUC_SUPERUSER_ONLY);
 
-	DefineCustomVariable("duckdb.motherduck_postgres_database", "Which database to enable MotherDuck support in",
-	                     &duckdb_motherduck_postgres_database, PGC_POSTMASTER, GUC_SUPERUSER_ONLY);
-
 	DefineCustomVariable("duckdb.motherduck_default_database",
 	                     "Which database in MotherDuck to designate as default (in place of my_db)",
 	                     &duckdb_motherduck_default_database, PGC_POSTMASTER, GUC_SUPERUSER_ONLY);

src/pgduckdb_background_worker.cpp

@@ -27,6 +27,7 @@ extern "C" {
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "executor/spi.h"
+#include "commands/dbcommands.h"
 #include "common/file_utils.h"
 #include "postmaster/bgworker.h"
 #include "postmaster/interrupt.h"
@@ -65,17 +66,20 @@ bool CanTakeLockForDatabase(Oid database_oid);
 extern "C" {
 
 PGDLLEXPORT void
-pgduckdb_background_worker_main(Datum /* main_arg */) {
-	elog(LOG, "started pg_duckdb background worker");
-	if (!CanTakeLockForDatabase(0)) {
-		elog(LOG, "pg_duckdb background worker: could not take lock for database '%u'. Will exit.", 0);
+pgduckdb_background_worker_main(Datum main_arg) {
+	Oid database_oid = DatumGetObjectId(main_arg);
+	if (!CanTakeLockForDatabase(database_oid)) {
+		elog(LOG, "pg_duckdb background worker: could not take lock for database '%u'. Will exit.", database_oid);
 		return;
 	}
+
+	elog(LOG, "started pg_duckdb background worker for database %u -- MyDB: %u", database_oid, MyDatabaseId);
+
 	// Set up a signal handler for SIGTERM
 	pqsignal(SIGTERM, die);
 	BackgroundWorkerUnblockSignals();
 
-	BackgroundWorkerInitializeConnection(duckdb_motherduck_postgres_database, NULL, 0);
+	BackgroundWorkerInitializeConnectionByOid(database_oid, InvalidOid, 0);
 
 	pgduckdb::doing_motherduck_sync = true;
 	is_background_worker = true;
@@ -221,7 +225,7 @@ StartBackgroundWorkerIfNeeded(void) {
 	snprintf(worker.bgw_function_name, BGW_MAXLEN, "pgduckdb_background_worker_main");
 	snprintf(worker.bgw_name, BGW_MAXLEN, PGDUCKDB_SYNC_WORKER_NAME);
 	worker.bgw_restart_time = 1;
-	worker.bgw_main_arg = (Datum)0;
+	worker.bgw_main_arg = ObjectIdGetDatum(MyDatabaseId);
 
 	RegisterDynamicBackgroundWorker(&worker, NULL);
 }
@@ -671,7 +675,8 @@ SyncMotherDuckCatalogsWithPg_Cpp(bool drop_with_cascade) {
 		}
 
 		/* The catalog version has changed, we need to sync the catalog */
-		elog(LOG, "Syncing MotherDuck catalog for database %s: %s", motherduck_db.c_str(), catalog_version.c_str());
+		elog(LOG, "Syncing MotherDuck catalog for database '%s' in '%s': %s", motherduck_db.c_str(),
+		     get_database_name(MyDatabaseId), catalog_version.c_str());
 
 		/*
 		 * Because of our SPI_commit_that_works_in_bgworker() workaround we need to
@@ -717,7 +722,6 @@ SyncMotherDuckCatalogsWithPg_Cpp(bool drop_with_cascade) {
 			}
 
 			std::string postgres_schema_name = PgSchemaName(motherduck_db, schema.name, is_default_db);
-
 			if (!CreateSchemaIfNotExists(postgres_schema_name.c_str(), is_default_db)) {
 				/* We failed to create the schema, so we skip the tables in it */
 				continue;

src/pgduckdb_metadata_cache.cpp

@@ -52,8 +52,6 @@ struct {
 	Oid extension_oid;
 	/* The OID of the duckdb Table Access Method */
 	Oid table_am_oid;
-	/* The OID of the duckdb.motherduck_postgres_database */
-	Oid motherduck_postgres_database_oid;
 	/* The OID of the duckdb.postgres_role */
 	Oid postgres_role_oid;
 	/*
@@ -180,8 +178,6 @@ IsExtensionRegistered() {
 
 		cache.table_am_oid = GetSysCacheOid1(AMNAME, Anum_pg_am_oid, CStringGetDatum("duckdb"));
 
-		cache.motherduck_postgres_database_oid = get_database_oid(duckdb_motherduck_postgres_database, false);
-
 		if (duckdb_postgres_role[0] != '\0') {
 			cache.postgres_role_oid =
 			    GetSysCacheOid1(AUTHNAME, Anum_pg_authid_oid, CStringGetDatum(duckdb_postgres_role));
@@ -258,7 +254,7 @@ IsMotherDuckTable(Relation relation) {
 
 bool
 IsMotherDuckEnabled() {
-	return IsMotherDuckEnabledAnywhere() && IsMotherDuckPostgresDatabase();
+	return IsMotherDuckEnabledAnywhere();
 }
 
 bool
@@ -270,12 +266,6 @@ IsMotherDuckEnabledAnywhere() {
 	return false;
 }
 
-bool
-IsMotherDuckPostgresDatabase() {
-	Assert(cache.valid);
-	return MyDatabaseId == cache.motherduck_postgres_database_oid;
-}
-
 Oid
 MotherDuckPostgresUser() {
 	Assert(cache.valid);

src/pgduckdb_ruleutils.cpp

@@ -217,8 +217,6 @@ pgduckdb_get_tabledef(Oid relation_oid) {
 		elog(ERROR, "Only TEMP tables are supported in DuckDB if MotherDuck support is not enabled");
 	} else if (relation->rd_rel->relpersistence != RELPERSISTENCE_PERMANENT) {
 		elog(ERROR, "Only TEMP and non-UNLOGGED tables are supported in DuckDB");
-	} else if (!pgduckdb::IsMotherDuckPostgresDatabase()) {
-		elog(ERROR, "MotherDuck tables must be created in the duckb.motherduck_postgres_database");
 	} else if (relation->rd_rel->relowner != pgduckdb::MotherDuckPostgresUser()) {
 		elog(ERROR, "MotherDuck tables must be created by the duckb.motherduck_postgres_user");
 	}