[olavloite]

Cloud Spanner requires a WHERE clause for all DELETE and UPDATE statements to prevent accidental table-wide data modifications.

Previously, unqualified queries and schema migration backfills relied on the low-level DB-API driver to rewrite SQL strings and append "WHERE 1=1". The Django backend now generates this clause directly during query compilation and migration execution.

Ensuring that Django generates compliant SQL on its own allows us to safely remove automatic SQL string rewriting from the DB-API driver in a future release without breaking Django applications.

BEGIN_COMMIT_OVERRIDE
fix(spanner-django): add WHERE 1=1 to unqualified DELETE and UPDATE
END_COMMIT_OVERRIDE

[gemini-code-assist]

Code Review

This pull request ensures that unqualified UPDATE and DELETE statements automatically append a dummy WHERE 1=1 clause in the Django Spanner backend. This is achieved by overriding the as_sql method in SQLDeleteCompiler and SQLUpdateCompiler, updating the schema editor's add_field method, and refining the add_dummy_where utility to handle edge cases safely. Extensive unit and mock server tests have been added to validate this behavior. The reviewer suggested using SQLGlotIR to safely wrap and modify SQL queries instead of manually parsing and manipulating the SQL string to avoid potential parsing issues.