Extract format_constraint truncation rules to ON CONFLICT

Fixed issue where a too-long constraint name rendered as part of the "ON
CONFLICT ON CONSTRAINT" element of the :class:`_postgresql.Insert`
construct due to naming convention generation would not correctly truncate
the name in the same way that it normally renders within a CREATE TABLE
statement, thus producing a non-matching and too-long constraint name.

Fixes: #6755
Change-Id: Ib27014a5ecbc9cd5861a396f8bb49fbc60bf49fe

diff --git a/doc/build/changelog/unreleased_14/6755.rst b/doc/build/changelog/unreleased_14/6755.rst
new file mode 100644 (file)
index 0000000..958ab0d
--- /dev/null
+++ b/doc/build/changelog/unreleased_14/6755.rst
@@ -0,0 +1,9 @@
+.. change::
+    :tags: bug, postgresql
+    :tickets: 6755
+
+    Fixed issue where a too-long constraint name rendered as part of the "ON
+    CONFLICT ON CONSTRAINT" element of the :class:`_postgresql.Insert`
+    construct due to naming convention generation would not correctly truncate
+    the name in the same way that it normally renders within a CREATE TABLE
+    statement, thus producing a non-matching and too-long constraint name.

diff --git a/lib/sqlalchemy/dialects/postgresql/base.py b/lib/sqlalchemy/dialects/postgresql/base.py
index ea2eda902f00d26ac0a2d7ffd2864ce221e95fde..48fc4fd711359eebbe161feb3b7b612f2ee5cea5 100644 (file)
--- a/lib/sqlalchemy/dialects/postgresql/base.py
+++ b/lib/sqlalchemy/dialects/postgresql/base.py
@@ -2322,8 +2322,16 @@ class PGCompiler(compiler.SQLCompiler):
     def _on_conflict_target(self, clause, **kw):
 
         if clause.constraint_target is not None:
-            target_text = "ON CONSTRAINT %s" % self.preparer.quote(
-                clause.constraint_target
+            # target may be a name of an Index, UniqueConstraint or
+            # ExcludeConstraint.  While there is a separate
+            # "max_identifier_length" for indexes, PostgreSQL uses the same
+            # length for all objects so we can use
+            # truncate_and_render_constraint_name
+            target_text = (
+                "ON CONSTRAINT %s"
+                % self.preparer.truncate_and_render_constraint_name(
+                    clause.constraint_target
+                )
             )
         elif clause.inferred_target_elements is not None:
             target_text = "(%s)" % ", ".join(

diff --git a/lib/sqlalchemy/sql/compiler.py b/lib/sqlalchemy/sql/compiler.py
index 4b3b2c293c6c81a11d643a375873e6757691e908..9ecd68412bc51c2e63e2ca57af7fc1da085ef86f 100644 (file)
--- a/lib/sqlalchemy/sql/compiler.py
+++ b/lib/sqlalchemy/sql/compiler.py
@@ -4961,20 +4961,41 @@ class IdentifierPreparer(object):
         else:
             name = constraint.name
 
+        if constraint.__visit_name__ == "index":
+            return self.truncate_and_render_index_name(
+                name, _alembic_quote=_alembic_quote
+            )
+        else:
+            return self.truncate_and_render_constraint_name(
+                name, _alembic_quote=_alembic_quote
+            )
+
+    def truncate_and_render_index_name(self, name, _alembic_quote=True):
+        # calculate these at format time so that ad-hoc changes
+        # to dialect.max_identifier_length etc. can be reflected
+        # as IdentifierPreparer is long lived
+        max_ = (
+            self.dialect.max_index_name_length
+            or self.dialect.max_identifier_length
+        )
+        return self._truncate_and_render_maxlen_name(
+            name, max_, _alembic_quote
+        )
+
+    def truncate_and_render_constraint_name(self, name, _alembic_quote=True):
+        # calculate these at format time so that ad-hoc changes
+        # to dialect.max_identifier_length etc. can be reflected
+        # as IdentifierPreparer is long lived
+        max_ = (
+            self.dialect.max_constraint_name_length
+            or self.dialect.max_identifier_length
+        )
+        return self._truncate_and_render_maxlen_name(
+            name, max_, _alembic_quote
+        )
+
+    def _truncate_and_render_maxlen_name(self, name, max_, _alembic_quote):
         if isinstance(name, elements._truncated_label):
-            # calculate these at format time so that ad-hoc changes
-            # to dialect.max_identifier_length etc. can be reflected
-            # as IdentifierPreparer is long lived
-            if constraint.__visit_name__ == "index":
-                max_ = (
-                    self.dialect.max_index_name_length
-                    or self.dialect.max_identifier_length
-                )
-            else:
-                max_ = (
-                    self.dialect.max_constraint_name_length
-                    or self.dialect.max_identifier_length
-                )
             if len(name) > max_:
                 name = name[0 : max_ - 8] + "_" + util.md5_hex(name)[-4:]
         else:

diff --git a/test/dialect/postgresql/test_compiler.py b/test/dialect/postgresql/test_compiler.py
index e48de9d21d7411f08e890e8aacdad5078a450967..73b3051f9d19c215dc95cdfe4df94ce89c271b3d 100644 (file)
--- a/test/dialect/postgresql/test_compiler.py
+++ b/test/dialect/postgresql/test_compiler.py
@@ -2351,6 +2351,32 @@ class InsertOnConflictTest(fixtures.TestBase, AssertsCompiledSQL):
             "DO NOTHING",
         )
 
+    def test_do_nothing_super_long_name_constraint_target(self):
+        """test #6755"""
+
+        m = MetaData(
+            naming_convention={"uq": "%(table_name)s_%(column_0_N_name)s_key"}
+        )
+
+        uq = UniqueConstraint("some_column_name_thats_really_really_long_too")
+        Table(
+            "some_table_name_thats_really_really",
+            m,
+            Column("some_column_name_thats_really_really_long_too", Integer),
+            uq,
+        )
+
+        i = insert(self.table1, values=dict(name="foo"))
+
+        i = i.on_conflict_do_nothing(constraint=uq)
+        self.assert_compile(
+            i,
+            "INSERT INTO mytable (name) VALUES (%(name)s) ON CONFLICT "
+            "ON CONSTRAINT "
+            "some_table_name_thats_really_really_some_column_name_th_f7ab "
+            "DO NOTHING",
+        )
+
     def test_do_nothing_quoted_named_constraint_target(self):
         """test #6696"""
         i = insert(self.table1, values=dict(name="foo"))