Add custom SQLAlchemy extensions for Postgres' string_agg.

diff --git a/daklib/daksql.py b/daklib/daksql.py
new file mode 100644 (file)
index 0000000..d2fe6b8
--- /dev/null
+++ b/daklib/daksql.py
@@ -0,0 +1,52 @@
+"""SQLAlchemy extensions for dak
+
+@copyright: 2014, Ansgar Burchardt <ansgar@debian.org>
+@license: GPL-2+
+"""
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+from sqlalchemy.ext.compiler import compiles
+from sqlalchemy.sql.expression import ColumnElement, ClauseElement, ClauseList, literal
+from sqlalchemy.types import Text
+from sqlalchemy.util import to_list
+
+class array_agg(ColumnElement):
+    def __init__(self, expr, order_by=None):
+        self.expr = ClauseElement(expr)
+        self.order_by = None
+        if order_by is not None:
+            self.order_by = ClauseList(*to_list(order_by))
+
+@compiles(array_agg)
+def compile_array_agg(element, compiler, **kw):
+    if element.order_by is not None:
+        return "ARRAY_AGG({0} ORDER BY {1})".format(compiler.process(element.expr), compiler.process(element.order_by))
+    return "ARRAY_AGG({0})".format(compiler.process(element.expr))
+
+class string_agg(ColumnElement):
+    type = Text()
+    def __init__(self, column, seperator, order_by=None):
+        self.column = ClauseList(*to_list(column))
+        self.seperator = literal(seperator)
+        self.order_by = None
+        if order_by is not None:
+            self.order_by = ClauseList(*to_list(order_by))
+
+@compiles(string_agg)
+def compile_string_agg(element, compiler, **kw):
+    if element.order_by is not None:
+        return "STRING_AGG({0}, {1} ORDER BY {2})".format(compiler.process(element.column), compiler.process(element.seperator), compiler.process(element.order_by))
+    return "STRING_AGG({0}, {1})".format(compiler.process(element.column), compiler.process(element.seperator))