Update constraint names generation

Fixes databricks#24

Author: pbtsrc

pgsqlite/pgsqlite.py

@@ -181,7 +181,9 @@ def __init__(self, sqlite_filename: str, pg_conninfo: str, show_sample_data: boo
         self.max_import_concurrency = max_import_concurrency
         db = Database(self.sqlite_filename)
         self._tables = {t.name: ParsedTable(t) for t in db.tables}
-
+        self._constr_names = []
+        self._constr_names_counter = 0
+        
     @property
     def tables(self):
         return self._tables.values()
@@ -237,6 +239,11 @@ def get_table_sql(self, table: ParsedTable) -> SQL:
             transpiled_pks_to_add = [table.get_transpiled_colname(pk) for pk in pks_to_add]
             all_column_sql = all_column_sql + SQL(",\n")
             pk_name = f"PK_{table.source_name}_" + ''.join(pks_to_add)
+            if pk_name in self._constr_names:
+                self._constr_names_counter += 1
+                pk_name = f"{pk_name}_{self._constr_names_counter}"
+            else:
+                self._constr_names.append(pk_name)            
             pk_sql = SQL("    CONSTRAINT {pk_name} PRIMARY KEY ({pks})").format(
                     table_name=Identifier(table.transpiled_name),
                     pk_name=Identifier(pk_name), pks=SQL(", ").join(
@@ -269,6 +276,11 @@ def get_fk_sql(self, table: ParsedTable) -> SQL:
         # create the foreign keys after the tables to avoid having to figure out the dep graph
         for fk in table.src_table.foreign_keys:
             fk_name = f"FK_{fk.other_table}_{fk.other_column}"
+            if fk_name in self._constr_names:
+                self._constr_names_counter += 1
+                fk_name = f"{fk_name}_{self._constr_names_counter}"  
+            else:
+                self._constr_names.append(fk_name)                
             fk_sql = SQL("ALTER TABLE {table_name} ADD CONSTRAINT {key_name}  FOREIGN KEY ({column}) REFERENCES {other_table} ({other_column})").format(
                 table_name=Identifier(table.transpiled_name),
                 column=Identifier(table.get_transpiled_colname(fk.column)),
@@ -586,4 +598,4 @@ async def create_all_indexes():
     logger.debug(json.dumps(loader.get_summary(), indent=2))
 
     if args.drop_tables_after_import:
-        loader._drop_tables()
+        loader._drop_tables()