04/25 fix phase12

migrations/versions/phase12_performance_indexes.py

@@ -21,10 +21,24 @@ DB index, causing full table scans as row counts grow:
     - assigned_to     — filtered for inspector-scoped views
     - reported_at     — used for ordering
 
-All indexes are created with IF NOT EXISTS so the migration is safe to re-run.
+Existence checks use information_schema so the migration is safe to re-run
+on any MySQL version (compatible back to 5.7).
 """
 
 from alembic import op
+from sqlalchemy import text
+
+
+def _index_exists(conn, table: str, index_name: str) -> bool:
+    """Return True if the named index already exists on the given table."""
+    result = conn.execute(text(
+        "SELECT COUNT(*) FROM information_schema.statistics "
+        "WHERE table_schema = DATABASE() "
+        "  AND table_name   = :table "
+        "  AND index_name   = :index"
+    ), {'table': table, 'index': index_name})
+    return result.scalar() > 0
+
 
 revision      = 'phase12_performance_indexes'
 down_revision = 'phase11_director_role'
@@ -32,51 +46,32 @@ branch_labels = None
 depends_on    = None
 
 
-def upgrade():
+# (table, index_name, column)
-    # ── inspections ──────────────────────────────────────────────────────────
+INDEXES = [
-    op.execute(
+    ('inspections', 'ix_inspections_status',          'status'),
-        "CREATE INDEX IF NOT EXISTS ix_inspections_status "
+    ('inspections', 'ix_inspections_facility_id',     'facility_id'),
-        "ON inspections (status)"
+    ('inspections', 'ix_inspections_inspector_id',    'inspector_id'),
-    )
+    ('inspections', 'ix_inspections_inspection_date', 'inspection_date'),
-    op.execute(
+    ('issues',      'ix_issues_status',               'status'),
-        "CREATE INDEX IF NOT EXISTS ix_inspections_facility_id "
+    ('issues',      'ix_issues_severity',             'severity'),
-        "ON inspections (facility_id)"
+    ('issues',      'ix_issues_assigned_to',          'assigned_to'),
-    )
+    ('issues',      'ix_issues_reported_at',          'reported_at'),
-    op.execute(
+]
-        "CREATE INDEX IF NOT EXISTS ix_inspections_inspector_id "
-        "ON inspections (inspector_id)"
-    )
-    op.execute(
-        "CREATE INDEX IF NOT EXISTS ix_inspections_inspection_date "
-        "ON inspections (inspection_date)"
-    )
 
-    # ── issues ───────────────────────────────────────────────────────────────
+
-    op.execute(
+def upgrade():
-        "CREATE INDEX IF NOT EXISTS ix_issues_status "
+    conn = op.get_bind()
-        "ON issues (status)"
+    for table, index_name, column in INDEXES:
-    )
+        if not _index_exists(conn, table, index_name):
-    op.execute(
+            op.execute(text(
-        "CREATE INDEX IF NOT EXISTS ix_issues_severity "
+                f'CREATE INDEX {index_name} ON {table} ({column})'
-        "ON issues (severity)"
+            ))
-    )
-    op.execute(
-        "CREATE INDEX IF NOT EXISTS ix_issues_assigned_to "
-        "ON issues (assigned_to)"
-    )
-    op.execute(
-        "CREATE INDEX IF NOT EXISTS ix_issues_reported_at "
-        "ON issues (reported_at)"
-    )
 
 
 def downgrade():
-    op.execute("DROP INDEX IF EXISTS ix_inspections_status      ON inspections")
+    conn = op.get_bind()
-    op.execute("DROP INDEX IF EXISTS ix_inspections_facility_id ON inspections")
+    for table, index_name, _column in INDEXES:
-    op.execute("DROP INDEX IF EXISTS ix_inspections_inspector_id ON inspections")
+        if _index_exists(conn, table, index_name):
-    op.execute("DROP INDEX IF EXISTS ix_inspections_inspection_date ON inspections")
+            op.execute(text(
-
+                f'DROP INDEX {index_name} ON {table}'
-    op.execute("DROP INDEX IF EXISTS ix_issues_status      ON issues")
+            ))
-    op.execute("DROP INDEX IF EXISTS ix_issues_severity    ON issues")
-    op.execute("DROP INDEX IF EXISTS ix_issues_assigned_to ON issues")
-    op.execute("DROP INDEX IF EXISTS ix_issues_reported_at ON issues")