improve drop_index (add if_exists)

pydal/adapters/base.py

@@ -966,8 +966,8 @@ def create_index(self, table, index_name, *fields, **kwargs):
             raise RuntimeError(err % (index_name, str(e), sql))
         return True
 
-    def drop_index(self, table, index_name):
-        sql = self.dialect.drop_index(index_name, table)
+    def drop_index(self, table, index_name, if_exists = False):
+        sql = self.dialect.drop_index(index_name, table, if_exists)
         try:
             self.execute(sql)
             self.commit()

pydal/dialects/base.py

@@ -606,8 +606,9 @@ def create_index(self, name, table, expressions, unique=False):
             )
         return rv
 
-    def drop_index(self, name, table):
-        return "DROP INDEX %s;" % self.quote(name)
+    def drop_index(self, name, table, if_exists = False):
+        if_exists = "IF EXISTS " if if_exists else ""
+        return "DROP INDEX %s%s;" % (if_exists, self.quote(name))
 
     def constraint_name(self, table, fieldname):
         return "%s_%s__constraint" % (table, fieldname)

pydal/dialects/mssql.py

@@ -237,7 +237,7 @@ def primary_key(self, key):
     def concat_add(self, tablename):
         return "; ALTER TABLE %s ADD " % tablename
 
-    def drop_index(self, name, table):
+    def drop_index(self, name, table, if_exists = False):
         return "DROP INDEX %s ON %s;" % (self.quote(name), table._rname)
 
     def st_astext(self, first, query_env={}):

pydal/dialects/mysql.py

@@ -107,5 +107,5 @@ def drop_table(self, table, mode):
             "SET FOREIGN_KEY_CHECKS=1;",
         ]
 
-    def drop_index(self, name, table):
+    def drop_index(self, name, table, if_exists = False):
         return "DROP INDEX %s ON %s;" % (self.quote(name), table._rname)

pydal/objects.py

@@ -1221,8 +1221,8 @@ def on(self, query):
     def create_index(self, name, *fields, **kwargs):
         return self._db._adapter.create_index(self, name, *fields, **kwargs)
 
-    def drop_index(self, name):
-        return self._db._adapter.drop_index(self, name)
+    def drop_index(self, name, if_exists = False):
+        return self._db._adapter.drop_index(self, name, if_exists)
 
 
 class Select(BasicStorage):
@@ -1502,7 +1502,7 @@ def __invert__(self):
 
     def __add__(self, other):
         return Expression(self.db, self._dialect.add, self, other, self.type)
-    
+
     def __radd__(self, other):
         if not hasattr(other, "type"):
             if isinstance(other, str):