[DBMON-5463] Switch sql index query resolution over to a static version check (#20514)

* Switch over to a static version check

* Add changelog

Author: eric-weaver

mysql/changelog.d/20514.fixed

@@ -0,0 +1 @@
+Avoid querying INFORMATION_SCHEMA.COLUMNS in favor of a static version check

mysql/datadog_checks/mysql/databases_data.py

@@ -20,11 +20,9 @@
     SQL_COLUMNS,
     SQL_DATABASES,
     SQL_FOREIGN_KEYS,
-    SQL_INDEXES,
-    SQL_INDEXES_8_0_13,
-    SQL_INDEXES_EXPRESSION_COLUMN_CHECK,
     SQL_PARTITION,
     SQL_TABLES,
+    get_indexes_query,
 )
 
 from .util import get_list_chunks
@@ -169,8 +167,7 @@ def _cursor_run(self, cursor, query, params=None):
     @tracked_method(agent_check_getter=agent_check_getter)
     def _fetch_database_data(self, cursor, start_time, db_name):
         tables = self._get_tables(db_name, cursor)
-        tables_chunks = list(get_list_chunks(tables, self.TABLES_CHUNK_SIZE))
-        for tables_chunk in tables_chunks:
+        for tables_chunk in get_list_chunks(tables, self.TABLES_CHUNK_SIZE):
             schema_collection_elapsed_time = time.time() - start_time
             if schema_collection_elapsed_time > self._max_execution_time:
                 self._data_submitter.submit()
@@ -357,12 +354,7 @@ def _populate_with_columns_data(self, table_name_to_table_index, table_list, tab
 
     @tracked_method(agent_check_getter=agent_check_getter)
     def _populate_with_index_data(self, table_name_to_table_index, table_list, table_names, db_name, cursor):
-        self._cursor_run(cursor, query=SQL_INDEXES_EXPRESSION_COLUMN_CHECK)
-        query = (
-            SQL_INDEXES_8_0_13.format(table_names)
-            if cursor.fetchone()["column_count"] > 0
-            else SQL_INDEXES.format(table_names)
-        )
+        query = get_indexes_query(self._check.version, self._check.is_mariadb, table_names)
         self._cursor_run(cursor, query=query, params=db_name)
         rows = cursor.fetchall()
         if not rows:

mysql/datadog_checks/mysql/queries.py

@@ -120,14 +120,6 @@
 WHERE table_schema = %s AND table_name IN ({});
 """
 
-SQL_INDEXES_EXPRESSION_COLUMN_CHECK = """
-    SELECT COUNT(*) as column_count
-    FROM INFORMATION_SCHEMA.COLUMNS
-    WHERE TABLE_SCHEMA = 'information_schema'
-      AND TABLE_NAME = 'STATISTICS'
-      AND COLUMN_NAME = 'EXPRESSION';
-"""
-
 SQL_INDEXES = """\
 SELECT
     table_name as `table_name`,
@@ -268,3 +260,15 @@ def show_primary_replication_status_query(version, is_mariadb):
         return "SHOW BINARY LOG STATUS;"
     else:
         return "SHOW MASTER STATUS;"
+
+
+def get_indexes_query(version, is_mariadb, table_names):
+    """
+    Get the appropriate indexes query based on MySQL version and flavor.
+    The EXPRESSION column was introduced in MySQL 8.0.13 for functional indexes.
+    MariaDB doesn't support functional indexes.
+    """
+    if not is_mariadb and version.version_compatible((8, 0, 13)):
+        return SQL_INDEXES_8_0_13.format(table_names)
+    else:
+        return SQL_INDEXES.format(table_names)