- The MySQL CAST compilation now takes into account aspects of a string

type such as "charset" and "collation".  While MySQL wants all character-
based CAST calls to use the CHAR type, we now create a real CHAR
object at CAST time and copy over all the parameters it has, so that
an expression like ``cast(x, mysql.TEXT(charset='utf8'))`` will
render ``CAST(t.col AS CHAR CHARACTER SET utf8)``.

- Added new "unicode returns" detection to the MySQL dialect and
to the default dialect system overall, such that any dialect
can add extra "tests" to the on-first-connect "does this DBAPI
return unicode directly?" detection. In this case, we are
adding a check specifically against the "utf8" encoding with
an explicit "utf8_bin" collation type (after checking that
this collation is available) to test for some buggy unicode
behavior observed with MySQLdb version 1.2.3.  While MySQLdb
has resolved this issue as of 1.2.4, the check here should
guard against regressions.  The change also allows the "unicode"
checks to log in the engine logs, which was not previously
the case. [ticket:2906]

1 files changed, 25 insertions, 9 deletions

diff --git a/lib/sqlalchemy/dialects/mysql/base.py b/lib/sqlalchemy/dialects/mysql/base.py
index a3942e89c..22675e592 100644
--- a/lib/sqlalchemy/dialects/mysql/base.py
+++ b/lib/sqlalchemy/dialects/mysql/base.py
@@ -976,6 +976,25 @@ class CHAR(_StringType, sqltypes.CHAR):
         """
         super(CHAR, self).__init__(length=length, **kwargs)
 
+    @classmethod
+    def _adapt_string_for_cast(self, type_):
+        # copy the given string type into a CHAR
+        # for the purposes of rendering a CAST expression
+        type_ = sqltypes.to_instance(type_)
+        if isinstance(type_, sqltypes.CHAR):
+            return type_
+        elif isinstance(type_, _StringType):
+            return CHAR(
+                length=type_.length,
+                charset=type_.charset,
+                collation=type_.collation,
+                ascii=type_.ascii,
+                binary=type_.binary,
+                unicode=type_.unicode,
+                national=False # not supported in CAST
+            )
+        else:
+            return CHAR(length=type_.length)
 
 class NVARCHAR(_StringType, sqltypes.NVARCHAR):
     """MySQL NVARCHAR type.
@@ -1397,14 +1416,9 @@ class MySQLCompiler(compiler.SQLCompiler):
         elif isinstance(type_, (sqltypes.DECIMAL, sqltypes.DateTime,
                                             sqltypes.Date, sqltypes.Time)):
             return self.dialect.type_compiler.process(type_)
-        elif isinstance(type_, sqltypes.Text):
-            return 'CHAR'
-        elif (isinstance(type_, sqltypes.String) and not
-              isinstance(type_, (ENUM, SET))):
-            if getattr(type_, 'length'):
-                return 'CHAR(%s)' % type_.length
-            else:
-                return 'CHAR'
+        elif isinstance(type_, sqltypes.String) and not isinstance(type_, (ENUM, SET)):
+            adapted = CHAR._adapt_string_for_cast(type_)
+            return self.dialect.type_compiler.process(adapted)
         elif isinstance(type_, sqltypes._Binary):
             return 'BINARY'
         elif isinstance(type_, sqltypes.NUMERIC):
@@ -2165,7 +2179,6 @@ class MySQLDialect(default.DefaultDialect):
                 rs.close()
 
     def initialize(self, connection):
-        default.DefaultDialect.initialize(self, connection)
         self._connection_charset = self._detect_charset(connection)
         self._detect_ansiquotes(connection)
         if self._server_ansiquotes:
@@ -2174,6 +2187,8 @@ class MySQLDialect(default.DefaultDialect):
             self.identifier_preparer = self.preparer(self,
                                 server_ansiquotes=self._server_ansiquotes)
 
+        default.DefaultDialect.initialize(self, connection)
+
     @property
     def _supports_cast(self):
         return self.server_version_info is None or \
@@ -2443,6 +2458,7 @@ class MySQLDialect(default.DefaultDialect):
         # as of MySQL 5.0.1
         self._backslash_escapes = 'NO_BACKSLASH_ESCAPES' not in mode
 
+
     def _show_create_table(self, connection, table, charset=None,
                            full_name=None):
         """Run SHOW CREATE TABLE for a ``Table``."""