feat(spanner): add Google Cloud Spanner support

crates/dbx-core/src/sql_dialect/capabilities.rs

@@ -63,6 +63,11 @@ pub fn is_schema_aware(database_type: DatabaseType) -> bool {
             | DatabaseType::Sqlite
             | DatabaseType::DuckDb
             | DatabaseType::Iris
+            // Spanner supports named schemas; the PostgreSQL dialect defaults to `public`.
+            // GoogleSQL's default schema is the empty string, which the blank-schema filters
+            // in `qualified_table_name` / `table_data_qualified_table_name` drop along with
+            // the dot separator (`` `s`.`t` `` with an empty `s` is a Spanner syntax error).
+            | DatabaseType::Spanner
     )
 }
 

crates/dbx-core/src/sql_dialect/ddl_profile.rs

@@ -670,9 +670,8 @@ pub fn profile_for(db_type: DatabaseType) -> DdlDialectProfile {
         ClickHouse => clickhouse_profile(),
 
         DuckDb | Questdb | SapHana | Teradata | Snowflake | Trino | PrestoSql | Hive | Kyuubi | Impala | Spark
-        | Db2 | Informix | Bigquery | Kylin | Ignite | Ignite3 | Oscar | Tdengine | Iotdb | Databricks | Jdbc => {
-            conservative_ansi(db_type)
-        }
+        | Db2 | Informix | Bigquery | Spanner | Kylin | Ignite | Ignite3 | Oscar | Tdengine | Iotdb | Databricks
+        | Jdbc => conservative_ansi(db_type),
 
         // Non-tabular / not applicable for relational CREATE TABLE
         Redis | MongoDb | DynamoDb | Elasticsearch | Easysearch | Meilisearch | Qdrant | Milvus | Weaviate

crates/dbx-core/src/sql_dialect/identifiers.rs

@@ -136,6 +136,11 @@ pub fn quote_table_identifier(database_type: Option<DatabaseType>, name: &str) -
             | DatabaseType::Tdengine
             | DatabaseType::Access
             | DatabaseType::Bigquery
+            // GoogleSQL (Spanner's default dialect) quotes identifiers with backticks;
+            // double quotes are string literals there, so `SELECT * FROM "users"` is a
+            // syntax error. PostgreSQL-dialect Spanner databases override this through
+            // the identifier quote reported by the agent on connect.
+            | DatabaseType::Spanner
             | DatabaseType::Questdb,
         ) => {
             format!("`{}`", name.replace('`', "``"))

crates/dbx-core/src/sql_dialect/table_select.rs

@@ -385,6 +385,11 @@ pub(crate) fn uses_connection_identifier_quote(
     identifier_quote: Option<&str>,
 ) -> bool {
     database_type == Some(DatabaseType::Kingbase)
+        // Spanner is dual-dialect: GoogleSQL uses backticks, the PostgreSQL dialect uses
+        // double quotes, and only the connected agent knows which. Unconditional like
+        // Kingbase — when no quote was reported the callers fall back to
+        // `quote_table_identifier`, whose static mapping is GoogleSQL-correct.
+        || database_type == Some(DatabaseType::Spanner)
         || (database_type == Some(DatabaseType::Informix) && identifier_quote.is_some())
         || (matches!(database_type, Some(DatabaseType::Gaussdb | DatabaseType::OpenGauss | DatabaseType::Postgres))
             && identifier_quote.is_some())

crates/dbx-core/src/sql_dialect/tests.rs

@@ -34,6 +34,37 @@ fn quotes_identifiers_by_database_type() {
     assert_eq!(quote_table_identifier(Some(DatabaseType::Jdbc), "users_1"), "users_1");
     assert_eq!(quote_table_identifier(Some(DatabaseType::Jdbc), "user name"), "user name");
     assert_eq!(quote_table_identifier(Some(DatabaseType::Iotdb), "root.test.device2"), "root.test.device2");
+    assert_eq!(quote_table_identifier(Some(DatabaseType::Spanner), "user`name"), "`user``name`");
+}
+
+/// Spanner databases are created in one of two immutable dialects. The connected
+/// agent reports the correct identifier quote; when it is missing the static mapping
+/// must fall back to GoogleSQL (backticks), because GoogleSQL treats double quotes as
+/// string literals and would reject `SELECT * FROM "users"`.
+#[test]
+fn quotes_spanner_identifiers_by_connection_dialect() {
+    // GoogleSQL dialect: agent reports a backtick.
+    assert_eq!(quote_table_data_identifier(Some(DatabaseType::Spanner), "order", Some("`")), "`order`");
+    assert_eq!(quote_table_data_identifier(Some(DatabaseType::Spanner), "user`name", Some("`")), "`user``name`");
+
+    // PostgreSQL dialect: agent reports a double quote.
+    assert_eq!(quote_table_data_identifier(Some(DatabaseType::Spanner), "order", Some("\"")), "\"order\"");
+    assert_eq!(quote_table_data_identifier(Some(DatabaseType::Spanner), "user\"name", Some("\"")), "\"user\"\"name\"");
+
+    // No quote reported (metadata probe failed / caller outside the desktop store):
+    // fall back to the GoogleSQL default rather than the ANSI double quote.
+    assert_eq!(quote_table_data_identifier(Some(DatabaseType::Spanner), "order", None), "`order`");
+
+    // GoogleSQL's default schema is the empty string and must not produce `` ``.`t` ``,
+    // which Spanner rejects with `Invalid empty identifier`.
+    assert_eq!(
+        table_data_qualified_table_name(Some(DatabaseType::Spanner), Some(""), "singers", Some("`")),
+        "`singers`"
+    );
+    assert_eq!(
+        table_data_qualified_table_name(Some(DatabaseType::Spanner), Some("public"), "singers", Some("\"")),
+        "\"public\".\"singers\""
+    );
 }
 
 #[test]
@@ -82,6 +113,11 @@ fn qualifies_schema_only_for_schema_aware_databases() {
     assert_eq!(qualified_table_name(Some(DatabaseType::Informix), Some("xtdpcky"), "users"), "xtdpcky.users");
     assert_eq!(qualified_table_name(Some(DatabaseType::Sqlite), Some("analytics"), "users"), "\"analytics\".\"users\"");
     assert_eq!(qualified_table_name(Some(DatabaseType::Jdbc), Some("cbsdw_dwd"), "dwd_test_df"), "dwd_test_df");
+    // GoogleSQL's default schema is the empty string: the qualifier (and its dot) must be
+    // dropped entirely, otherwise Spanner reports `Invalid empty identifier`.
+    assert_eq!(qualified_table_name(Some(DatabaseType::Spanner), Some(""), "users"), "`users`");
+    assert_eq!(qualified_table_name(Some(DatabaseType::Spanner), None, "users"), "`users`");
+    assert_eq!(qualified_table_name(Some(DatabaseType::Spanner), Some("public"), "users"), "`public`.`users`");
     assert_eq!(qualified_table_name(Some(DatabaseType::Iotdb), Some("root.test"), "device2"), "root.test.device2");
     assert_eq!(
         qualified_table_name(Some(DatabaseType::Iotdb), Some("root.test"), "root.test.device2"),
@@ -127,6 +163,8 @@ fn maps_table_pagination_strategy_by_database_type() {
         TablePaginationStrategy::Unbounded
     );
     assert_eq!(table_pagination_strategy(Some(DatabaseType::Jdbc)), TablePaginationStrategy::AgentMaxRows);
+    // Both Spanner dialects support `LIMIT n OFFSET m`; pin the fallback.
+    assert_eq!(table_pagination_strategy(Some(DatabaseType::Spanner)), TablePaginationStrategy::LimitOffset);
     assert_eq!(table_pagination_strategy(None), TablePaginationStrategy::LimitOffset);
 }