merge from branches/clauseelement-nonzero

adds a __nonzero__ to _BinaryExpression to avoid faulty comparisons during hash
collisions (which only occur on Jython)
fixes #1547

5 files changed, 6 insertions, 6 deletions

diff --git a/lib/sqlalchemy/dialects/firebird/base.py b/lib/sqlalchemy/dialects/firebird/base.py
index 71b5e5cdc..7b0007b68 100644
--- a/lib/sqlalchemy/dialects/firebird/base.py
+++ b/lib/sqlalchemy/dialects/firebird/base.py
@@ -221,7 +221,7 @@ class FBCompiler(sql.compiler.SQLCompiler):
     visit_char_length_func = visit_length_func
 
     def function_argspec(self, func, **kw):
-        if func.clauses:
+        if func.clauses is not None and len(func.clauses):
             return self.process(func.clause_expr)
         else:
             return ""
diff --git a/lib/sqlalchemy/dialects/mssql/base.py b/lib/sqlalchemy/dialects/mssql/base.py
index 813f42cbb..b190af7b2 100644
--- a/lib/sqlalchemy/dialects/mssql/base.py
+++ b/lib/sqlalchemy/dialects/mssql/base.py
@@ -1075,7 +1075,7 @@ class MSDDLCompiler(compiler.DDLCompiler):
             else:
                 colspec += " NULL"
         
-        if not column.table:
+        if column.table is None:
             raise exc.InvalidRequestError("mssql requires Table-bound columns in order to generate DDL")
             
         seq_col = column.table._autoincrement_column
diff --git a/lib/sqlalchemy/dialects/mysql/base.py b/lib/sqlalchemy/dialects/mysql/base.py
index aa616efdf..8408e19ed 100644
--- a/lib/sqlalchemy/dialects/mysql/base.py
+++ b/lib/sqlalchemy/dialects/mysql/base.py
@@ -1300,7 +1300,7 @@ class MySQLCompiler(compiler.SQLCompiler):
         text = "UPDATE " + self.preparer.format_table(update_stmt.table) + \
                 " SET " + ', '.join(["%s=%s" % (self.preparer.format_column(c[0]), c[1]) for c in colparams])
 
-        if update_stmt._whereclause:
+        if update_stmt._whereclause is not None:
             text += " WHERE " + self.process(update_stmt._whereclause)
 
         limit = update_stmt.kwargs.get('mysql_limit', None)
diff --git a/lib/sqlalchemy/dialects/oracle/base.py b/lib/sqlalchemy/dialects/oracle/base.py
index 454be70f8..c14151515 100644
--- a/lib/sqlalchemy/dialects/oracle/base.py
+++ b/lib/sqlalchemy/dialects/oracle/base.py
@@ -365,7 +365,7 @@ class OracleCompiler(compiler.SQLCompiler):
 
                 froms = select._get_display_froms(existingfroms)
                 whereclause = self._get_nonansi_join_whereclause(froms)
-                if whereclause:
+                if whereclause is not None:
                     select = select.where(whereclause)
                     select._oracle_visit = True
 
diff --git a/lib/sqlalchemy/dialects/postgresql/base.py b/lib/sqlalchemy/dialects/postgresql/base.py
index a6fa21f99..78ea1a8fc 100644
--- a/lib/sqlalchemy/dialects/postgresql/base.py
+++ b/lib/sqlalchemy/dialects/postgresql/base.py
@@ -240,8 +240,8 @@ class PGCompiler(compiler.SQLCompiler):
         return text
 
     def get_select_precolumns(self, select):
-        if select._distinct:
-            if isinstance(select._distinct, bool):
+        if select._distinct is not False:
+            if select._distinct is True:
                 return "DISTINCT "
             elif isinstance(select._distinct, (list, tuple)):
                 return "DISTINCT ON (" + ', '.join(