Fix create drop table if exists (#75)

* Fix "DROP TABLE IF EXISTS"

* Fix "CREATE TABLE IF NOT EXISTS"

Author: nielsreijers

mysql_ch_replicator/clickhouse_api.py

@@ -14,7 +14,7 @@
 
 
 CREATE_TABLE_QUERY = '''
-CREATE TABLE {db_name}.{table_name}
+CREATE TABLE {if_not_exists} {db_name}.{table_name}
 (
 {fields},
     `_version` UInt64,
@@ -165,6 +165,7 @@ def create_table(self, structure: TableStructure, additional_indexes: list | Non
             primary_key = f'({primary_key})'
 
         query = CREATE_TABLE_QUERY.format(**{
+            'if_not_exists': 'IF NOT EXISTS' if structure.if_not_exists else '',
             'db_name': self.database,
             'table_name': structure.table_name,
             'fields': fields,

mysql_ch_replicator/converter.py

@@ -262,6 +262,7 @@ def convert_field_type(self, mysql_type, mysql_parameters):
     def convert_table_structure(self, mysql_structure: TableStructure) -> TableStructure:
         clickhouse_structure = TableStructure()
         clickhouse_structure.table_name = mysql_structure.table_name
+        clickhouse_structure.if_not_exists = mysql_structure.if_not_exists
         for field in mysql_structure.fields:
             clickhouse_field_type = self.convert_field_type(field.field_type, field.parameters)
             clickhouse_structure.fields.append(TableField(

mysql_ch_replicator/db_replicator.py

@@ -499,17 +499,26 @@ def handle_drop_table_query(self, query, db_name):
         tokens = query.split()
         if tokens[0].lower() != 'drop' or tokens[1].lower() != 'table':
             raise Exception('wrong drop table query', query)
+
+        if_exists = (len(tokens) > 4 and
+                tokens[2].lower() == 'if' and
+                tokens[3].lower() == 'exists')
+        if if_exists:
+            del tokens[2:4]  # Remove the 'IF', 'EXISTS' tokens
+
         if len(tokens) != 3:
             raise Exception('wrong token count', query)
+
         table_name = tokens[2]
         if '.' in table_name:
             db_name, table_name = table_name.split('.')
             if db_name == self.database:
                 db_name = self.target_database
         table_name = strip_sql_name(table_name)
         db_name = strip_sql_name(db_name)
-        self.state.tables_structure.pop(table_name)
-        self.clickhouse_api.execute_command(f'DROP TABLE {db_name}.{table_name}')
+        if table_name in self.state.tables_structure:
+            self.state.tables_structure.pop(table_name)
+        self.clickhouse_api.execute_command(f'DROP TABLE {"IF EXISTS" if if_exists else ""} {db_name}.{table_name}')
 
     def log_stats_if_required(self):
         curr_time = time.time()