Cherry-pick: Fix: system.databases always shows data lake catalog databases

src/Interpreters/DatabaseCatalog.h

@@ -156,8 +156,10 @@ class DatabaseCatalog : boost::noncopyable, WithMutableContext
     /// In general case Datalake catalog is a some remote service which contains iceberg/delta tables.
     /// Sometimes this service charges money for requests. With this flag we explicitly protect ourself
     /// to not accidentally query external non-free service for some trivial things like
-    /// autocompletion hints or system.tables query. We have a setting which allow to show
+    /// autocompletion hints or system.tables / system.columns queries. We have a setting which allow to show
     /// these databases everywhere, but user must explicitly specify it.
+    /// Note: system.databases always passes with_datalake_catalogs = true because listing a database name
+    /// is purely local metadata and never requires calls to an external catalog service.
     Databases getDatabases(GetDatabasesOptions options) const;
 
     /// Same as getDatabase(const String & database_name), but if database_name is empty, current database of local_context is used

src/Interpreters/InterpreterShowTablesQuery.cpp

@@ -232,19 +232,15 @@ BlockIO InterpreterShowTablesQuery::execute()
     }
     auto rewritten_query = getRewrittenQuery();
     String database = getContext()->resolveDatabase(query.getFrom());
-    if (query.databases || DatabaseCatalog::instance().isDatalakeCatalog(database))
-    {
-        auto query_context = Context::createCopy(getContext());
-        query_context->makeQueryContext();
-        query_context->setCurrentQueryId("");
-        /// HACK To always show them in explicit "SHOW TABLES" queries
-        query_context->setSetting("show_data_lake_catalogs_in_system_tables", true);
-        return executeQuery(rewritten_query, std::move(query_context), QueryFlags{ .internal = true }).second;
-    }
-
     auto query_context = Context::createCopy(getContext());
     query_context->makeQueryContext();
     query_context->setCurrentQueryId("");
+    if (DatabaseCatalog::instance().isDatalakeCatalog(database))
+    {
+        /// HACK: force the setting so that system.tables includes tables from the requested data lake catalog.
+        /// system.databases already shows all catalogs unconditionally, so no override is needed for SHOW DATABASES.
+        query_context->setSetting("show_data_lake_catalogs_in_system_tables", true);
+    }
     return executeQuery(rewritten_query, std::move(query_context), QueryFlags{ .internal = true }).second;
 }
 

src/Storages/System/StorageSystemDatabases.cpp

@@ -12,7 +12,6 @@
 #include <Storages/System/StorageSystemDatabases.h>
 #include <Storages/VirtualColumnUtils.h>
 #include <Common/logger_useful.h>
-#include <Core/Settings.h>
 
 
 namespace DB
@@ -23,10 +22,6 @@ namespace ErrorCodes
     extern const int UNKNOWN_DATABASE;
 }
 
-namespace Setting
-{
-    extern const SettingsBool show_data_lake_catalogs_in_system_tables;
-}
 
 ColumnsDescription StorageSystemDatabases::getColumnsDescription()
 {
@@ -124,8 +119,10 @@ void StorageSystemDatabases::fillData(MutableColumns & res_columns, ContextPtr c
 {
     const auto access = context->getAccess();
     const bool need_to_check_access_for_databases = !access->isGranted(AccessType::SHOW_DATABASES);
-    const auto & settings = context->getSettingsRef();
-    const auto databases = DatabaseCatalog::instance().getDatabases(GetDatabasesOptions{.with_datalake_catalogs = settings[Setting::show_data_lake_catalogs_in_system_tables]});
+    /// Data lake catalog databases are always shown in system.databases regardless of show_data_lake_catalogs_in_system_tables.
+    /// Listing a database name is purely local metadata and never requires expensive calls to an external catalog service.
+    /// The setting only guards operations like system.tables / system.columns that enumerate a catalog's contents.
+    const auto databases = DatabaseCatalog::instance().getDatabases(GetDatabasesOptions{.with_datalake_catalogs = true});
     ColumnPtr filtered_databases_column = getFilteredDatabases(databases, predicate, context);
 
     for (size_t i = 0; i < filtered_databases_column->size(); ++i)

tests/integration/test_database_glue/test.py

@@ -657,9 +657,10 @@ def test_system_tables(started_cluster):
     assert int(node.query(f"SELECT count() FROM system.iceberg_history WHERE database = '{CATALOG_NAME}' and table ilike '%{root_namespace}%' SETTINGS show_data_lake_catalogs_in_system_tables = true").strip()) == 4
     assert int(node.query(f"SELECT count() FROM system.iceberg_history WHERE database = '{CATALOG_NAME}' and table ilike '%{root_namespace}%' SETTINGS show_data_lake_catalogs_in_system_tables = false").strip()) == 4
 
-    # system.databases
+    # system.databases always shows data lake catalog databases regardless of show_data_lake_catalogs_in_system_tables,
+    # because listing a database name is purely local metadata and never requires calls to an external catalog service.
     assert int(node.query(f"SELECT count() FROM system.databases WHERE name = '{CATALOG_NAME}' SETTINGS show_data_lake_catalogs_in_system_tables = true").strip()) == 1
-    assert int(node.query(f"SELECT count() FROM system.databases WHERE name = '{CATALOG_NAME}'").strip()) == 0
+    assert int(node.query(f"SELECT count() FROM system.databases WHERE name = '{CATALOG_NAME}' SETTINGS show_data_lake_catalogs_in_system_tables = false").strip()) == 1
 
     # system.columns
     assert int(node.query(f"SELECT count() FROM system.columns WHERE database = '{CATALOG_NAME}' and table ilike '%{root_namespace}%' SETTINGS show_data_lake_catalogs_in_system_tables = true").strip()) == 24