1. diana clarke
  2. sqlalchemy-1418


Mike Bayer  committed c6057b2

cast converted into its own ClauseElement so that it can have an explicit compilation
function in ANSICompiler
MySQLCompiler then skips most CAST calls since it only seems to support the standard syntax for Date
types; other types now a TODO for MySQL
then, polymorphic_union() function now CASTs null()s to the type corresponding to the columns in the UNION,
since postgres doesnt like mixing NULL with integer types
(long road for that .....)

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  • Tags rel_0_2_3

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Files changed (6)


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 information better [ticket:202]
 - if an object fails to be constructed, is not added to the 
 session [ticket:203]
+- CAST function has been made into its own clause object with
+its own compilation function in ansicompiler; allows MySQL
+to silently ignore most CAST calls since MySQL
+seems to only support the standard CAST syntax with Date types.  
+MySQL-compatible CAST support for strings, ints, etc. a TODO
 - big improvements to polymorphic inheritance behavior, enabling it

File lib/sqlalchemy/ansisql.py

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             self.strings[list] = "(" + string.join([self.get_str(c) for c in list.clauses], ' ') + ")"
             self.strings[list] = string.join([self.get_str(c) for c in list.clauses], ' ')
+    def visit_cast(self, cast):
+        if len(self.select_stack):
+            # not sure if we want to set the typemap here...
+            self.typemap.setdefault("CAST", cast.type)
+        self.strings[cast] = "CAST(%s AS %s)" % (self.strings[cast.clause],self.strings[cast.typeclause])
     def visit_function(self, func):
         if len(self.select_stack):
             self.typemap.setdefault(func.name, func.type)

File lib/sqlalchemy/databases/mysql.py

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 from sqlalchemy import sql,engine,schema,ansisql
 from sqlalchemy.engine import default
 import sqlalchemy.types as sqltypes
-import sqlalchemy.databases.information_schema as ischema
 import sqlalchemy.exceptions as exceptions
 class MySQLCompiler(ansisql.ANSICompiler):
+    def visit_cast(self, cast):
+        """hey ho MySQL supports almost no types at all for CAST"""
+        if (isinstance(cast.type, sqltypes.Date) or isinstance(cast.type, sqltypes.Time) or isinstance(cast.type, sqltypes.DateTime)):
+            return super(MySQLCompiler, self).visit_cast(cast)
+        else:
+            # so just skip the CAST altogether for now.
+            # TODO: put whatever MySQL does for CAST here.
+            self.strings[cast] = self.strings[cast.clause]
     def limit_clause(self, select):
         text = ""
         if select.limit is not None:

File lib/sqlalchemy/orm/util.py

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 def polymorphic_union(table_map, typecolname, aliasname='p_union'):
     colnames = util.Set()
     colnamemaps = {}
+    types = {}
     for key in table_map.keys():
         table = table_map[key]
         for c in table.c:
             m[c.name] = c
+            types[c.name] = c.type
         colnamemaps[table] = m
     def col(name, table):
             return colnamemaps[table][name]
         except KeyError:
-            return sql.null().label(name)
+            return sql.cast(sql.null(), types[name]).label(name)
     result = []
     for type, table in table_map.iteritems():

File lib/sqlalchemy/sql.py

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         cast(table.c.timestamp, DATE)
-    # handle non-column clauses (e.g. cast(1234, TEXT)
-    if not hasattr(clause, 'label'):
-        clause = literal(clause)
-    totype = sqltypes.to_instance(totype)
-    return Function('CAST', CompoundClause("AS", clause, TypeClause(totype)), type=totype, **kwargs)
+    return Cast(clause, totype, **kwargs)
 def exists(*args, **params):
     params['correlate'] = True
     s = select(*args, **params)
     def visit_clauselist(self, list):pass
     def visit_calculatedclause(self, calcclause):pass
     def visit_function(self, func):pass
+    def visit_cast(self, cast):pass
     def visit_label(self, label):pass
     def visit_typeclause(self, typeclause):pass
+class Cast(ColumnElement):
+    def __init__(self, clause, totype, **kwargs):
+        if not hasattr(clause, 'label'):
+            clause = literal(clause)
+        self.type = sqltypes.to_instance(totype)
+        self.clause = clause
+        self.typeclause = TypeClause(self.type)
+    def accept_visitor(self, visitor):
+        self.clause.accept_visitor(visitor)
+        self.typeclause.accept_visitor(visitor)
+        visitor.visit_cast(self)
+    def _get_from_objects(self):
+        return self.clause._get_from_objects()
 class FunctionGenerator(object):
     """generates Function objects based on getattr calls"""
     def __init__(self, engine=None):

File test/sql/select.py

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         check_results(postgres.dialect(), ['NUMERIC(10, 2)', 'NUMERIC(12, 9)', 'DATE', 'TEXT', 'VARCHAR(20)'], '%(literal)s')
         # then the Oracle engine
-#        check_results(oracle.OracleDialect(), ['NUMERIC(10, 2)', 'NUMERIC(12, 9)', 'DATE', 'CLOB', 'VARCHAR(20)'], ':literal')
+        check_results(oracle.dialect(), ['NUMERIC(10, 2)', 'NUMERIC(12, 9)', 'DATE', 'CLOB', 'VARCHAR(20)'], ':literal')
         # then the sqlite engine
         check_results(sqlite.dialect(), ['NUMERIC(10, 2)', 'NUMERIC(12, 9)', 'DATE', 'TEXT', 'VARCHAR(20)'], '?')
-        # and the MySQL engine
-        check_results(mysql.dialect(), ['NUMERIC(10, 2)', 'NUMERIC(12, 9)', 'DATE', 'TEXT', 'VARCHAR(20)'], '%s')
+        # MySQL seems to only support DATE types for cast
+        self.assertEqual(str(cast(tbl.c.ts, Date).compile(dialect=mysql.dialect())), 'CAST(casttest.ts AS DATE)')
+        self.assertEqual(str(cast(tbl.c.ts, Numeric).compile(dialect=mysql.dialect())), 'casttest.ts')
     def testdatebetween(self):
         import datetime