Add more zuul_ref indexes

This drops the (project, change) index in favor of several single-column
indexes that the dbms can combine as needed to quickly seek zuul_refs in queries.

Change-Id: I50ec1552e24c5aa634538ebb181da907898f1284

tests/unit/test_connection.py

@@ -114,7 +114,7 @@ class TestSQLConnectionMysql(ZuulTestCase):
         indexes_provides = insp.get_indexes(provides_table)
         indexes_build_event = insp.get_indexes(build_event_table)
 
-        self.assertEqual(3, len(indexes_ref))
+        self.assertEqual(8, len(indexes_ref))
         self.assertEqual(1, len(indexes_buildset))
         self.assertEqual(2, len(indexes_buildset_ref))
         self.assertEqual(4, len(indexes_build))

zuul/driver/sql/alembic/versions/3c1488fb137e_zuul_ref_indexes.py

@@ -0,0 +1,61 @@
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+"""zuul_ref_indexes
+
+Revision ID: 3c1488fb137e
+Revises: d0a269345a22
+Create Date: 2023-11-27 17:15:00.812075
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = '3c1488fb137e'
+down_revision = 'd0a269345a22'
+branch_labels = None
+depends_on = None
+
+from alembic import op
+
+REF_TABLE = 'zuul_ref'
+
+
+def upgrade(table_prefix=''):
+    prefixed_ref = table_prefix + REF_TABLE
+
+    op.create_index(f'{prefixed_ref}_project_idx',
+                    prefixed_ref,
+                    ['project'])
+    op.create_index(f'{prefixed_ref}_ref_idx',
+                    prefixed_ref,
+                    ['ref'])
+    op.create_index(f'{prefixed_ref}_branch_idx',
+                    prefixed_ref,
+                    ['branch'])
+    # Change is already indexed
+    op.create_index(f'{prefixed_ref}_patchset_idx',
+                    prefixed_ref,
+                    ['patchset'])
+    op.create_index(f'{prefixed_ref}_oldrev_idx',
+                    prefixed_ref,
+                    ['oldrev'])
+    op.create_index(f'{prefixed_ref}_newrev_idx',
+                    prefixed_ref,
+                    ['newrev'])
+
+    # Drop the project_change index and rely on separate indexes that
+    # may be merged by the dbms.
+    op.drop_index(f'{prefixed_ref}_project_change_idx', prefixed_ref)
+
+
+def downgrade():
+    raise Exception("Downgrades not supported")

zuul/driver/sql/sqlconnection.py

@@ -505,9 +505,13 @@ class SQLConnection(BaseConnection):
             newrev = sa.Column(SHAType(40), nullable=False)
             branch = sa.Column(sa.String(255), nullable=False)
 
-            sa.Index(self.table_prefix + 'zuul_ref_project_change_idx',
-                     project, change)
+            sa.Index(self.table_prefix + 'zuul_ref_project_idx', project)
+            sa.Index(self.table_prefix + 'zuul_ref_ref_idx', ref)
             sa.Index(self.table_prefix + 'zuul_ref_change_idx', change)
+            sa.Index(self.table_prefix + 'zuul_ref_patchset_idx', patchset)
+            sa.Index(self.table_prefix + 'zuul_ref_oldrev_idx', oldrev)
+            sa.Index(self.table_prefix + 'zuul_ref_newrev_idx', newrev)
+            sa.Index(self.table_prefix + 'zuul_ref_branch_idx', branch)
             sa.UniqueConstraint(
                 project, ref, change, patchset, oldrev, newrev,
                 name=self.table_prefix + 'zuul_ref_unique')