SYBASE: Added offset support

Fixes: #5294
### Description
Fix for https://github.com/sqlalchemy/sqlalchemy/issues/5294#issue-610311455

I tested it against our database (Adaptive Server Enterprise/16.0 SP02) with `pyodbc+sybase`

### Checklist

This pull request is:

- [x] A short code fix for #5294
- [x] Added tests.

Closes: #5312
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/5312
Pull-request-sha: f62c14825f2941fdd54ede17fd8d4f105a052e05

Change-Id: Ic716e17a6f654deef78781cefc3f16333cd725c3

diff --git a/doc/build/changelog/unreleased_13/5294.rst b/doc/build/changelog/unreleased_13/5294.rst
new file mode 100644 (file)
index 0000000..b564dc1
--- /dev/null
+++ b/doc/build/changelog/unreleased_13/5294.rst
@@ -0,0 +1,6 @@
+.. change::
+    :tags: change, sql, sybase
+    :tickets: 5294
+
+    Added ``.offset`` support to sybase dialect.
+    Pull request courtesy Alan D. Snow.

diff --git a/lib/sqlalchemy/dialects/sybase/base.py b/lib/sqlalchemy/dialects/sybase/base.py
index 77ebfac93808a9c818bcee17d16be3bd7937b780..e3848a9b2e0da1bc3b783c3ed42c5474d26fbce7 100644 (file)
--- a/lib/sqlalchemy/dialects/sybase/base.py
+++ b/lib/sqlalchemy/dialects/sybase/base.py
@@ -516,23 +516,18 @@ class SybaseSQLCompiler(compiler.SQLCompiler):
         {"doy": "dayofyear", "dow": "weekday", "milliseconds": "millisecond"},
     )
 
-    def get_select_precolumns(self, select, **kw):
-        s = select._distinct and "DISTINCT " or ""
-
-        if select._simple_int_limit and not select._offset:
-            kw["literal_execute"] = True
-            s += "TOP %s " % self.process(select._limit_clause, **kw)
-
-        if select._offset:
-            raise NotImplementedError("Sybase ASE does not support OFFSET")
-        return s
-
     def get_from_hint_text(self, table, text):
         return text
 
     def limit_clause(self, select, **kw):
-        # Limit in sybase is after the select keyword
-        return ""
+        text = ""
+        if select._limit_clause is not None:
+            text += " ROWS LIMIT " + self.process(select._limit_clause, **kw)
+        if select._offset_clause is not None:
+            if select._limit_clause is None:
+                text += " ROWS"
+            text += " OFFSET " + self.process(select._offset_clause, **kw)
+        return text
 
     def visit_extract(self, extract, **kw):
         field = self.extract_map.get(extract.field, extract.field)

diff --git a/test/dialect/test_sybase.py b/test/dialect/test_sybase.py
index b49c8cfb369a02eba4fa0d9cfc7f120e073cb345..f41fe4846d5ceb0a3825849af6627c431b340205 100644 (file)
--- a/test/dialect/test_sybase.py
+++ b/test/dialect/test_sybase.py
@@ -2,7 +2,6 @@ from sqlalchemy import extract
 from sqlalchemy import select
 from sqlalchemy import sql
 from sqlalchemy.dialects import sybase
-from sqlalchemy.testing import assert_raises_message
 from sqlalchemy.testing import AssertsCompiledSQL
 from sqlalchemy.testing import fixtures
 
@@ -28,15 +27,23 @@ class CompileTest(fixtures.TestBase, AssertsCompiledSQL):
                 'SELECT DATEPART("%s", t.col1) AS anon_1 FROM t' % subst,
             )
 
-    def test_offset_not_supported(self):
-        stmt = select([1]).offset(10)
-        assert_raises_message(
-            NotImplementedError,
-            "Sybase ASE does not support OFFSET",
-            stmt.compile,
-            dialect=self.__dialect__,
+    def test_limit_offset(self):
+        stmt = select([1]).limit(5).offset(6)
+        assert stmt.compile().params == {"param_1": 5, "param_2": 6}
+        self.assert_compile(
+            stmt, "SELECT 1 ROWS LIMIT :param_1 OFFSET :param_2"
         )
 
+    def test_offset(self):
+        stmt = select([1]).offset(10)
+        assert stmt.compile().params == {"param_1": 10}
+        self.assert_compile(stmt, "SELECT 1 ROWS OFFSET :param_1")
+
+    def test_limit(self):
+        stmt = select([1]).limit(5)
+        assert stmt.compile().params == {"param_1": 5}
+        self.assert_compile(stmt, "SELECT 1 ROWS LIMIT :param_1")
+
     def test_delete_extra_froms(self):
         t1 = sql.table("t1", sql.column("c1"))
         t2 = sql.table("t2", sql.column("c1"))