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-rw-r--r--lib/sqlalchemy/sql/compiler.py11
1 files changed, 10 insertions, 1 deletions
diff --git a/lib/sqlalchemy/sql/compiler.py b/lib/sqlalchemy/sql/compiler.py
index bc16b1429..23eff773c 100644
--- a/lib/sqlalchemy/sql/compiler.py
+++ b/lib/sqlalchemy/sql/compiler.py
@@ -2868,7 +2868,16 @@ class SQLCompiler(Compiled):
before column list.
"""
- return select._distinct and "DISTINCT " or ""
+ if select._distinct_on:
+ util.warn_deprecated(
+ "DISTINCT ON is currently supported only by the PostgreSQL "
+ "dialect. Use of DISTINCT ON for other backends is currently "
+ "silently ignored, however this usage is deprecated, and will "
+ "raise CompileError in a future release for all backends "
+ "that do not support this syntax.",
+ version="1.4",
+ )
+ return "DISTINCT " if select._distinct else ""
def group_by_clause(self, select, **kw):
"""allow dialects to customize how GROUP BY is rendered."""