tsapi-seriesdb-shared-sql/sql/migrate/migrate_drop_series_if_exists.sql

-- Migration: repair meta.drop_series_if_exists()
--
-- The function dropped a registered series without setting
-- application.dropping_series, so the prevent_direct_drop event trigger
-- rejected its own DROP:
--
--   Table series.X is registered in series and can only be dropped
--   using TimeseriesDB.drop_series()
--
-- Unlike meta.drop_series() and meta.drop_all_series(), which set the flag
-- correctly, this one never did -- so it always failed on exactly the case it
-- exists to handle. The Python API does not call it, which is why the defect
-- went unnoticed.
--
-- New databases pick this up from 05_procedures.sql. Run this against any
-- database initialised before the fix.
--
-- Safe to run more than once (CREATE OR REPLACE).

CREATE OR REPLACE FUNCTION meta.drop_series_if_exists(_table_name text, _schema_name text DEFAULT 'series'::text)
 RETURNS void
 LANGUAGE plpgsql
AS $function$
BEGIN
    -- Check if the series exists in series table
    IF EXISTS (
        SELECT 1 FROM meta.series
        WHERE "table_name" = _table_name
        AND "db_schema" = _schema_name
    ) THEN
        -- Signal the prevent_direct_drop event trigger that this DROP is
        -- coming from a sanctioned procedure. Without it the trigger rejects
        -- the statement below, because the table is registered in meta.series.
        -- Local to the transaction, so it cannot leak to later statements.
        PERFORM set_config('application.dropping_series', 'true', true);

        -- Drop the table
        EXECUTE format('DROP TABLE IF EXISTS %I.%I', _schema_name, _table_name);

        -- Remove from series table
        DELETE FROM meta.series
        WHERE "table_name" = _table_name
        AND "db_schema" = _schema_name;

        PERFORM set_config('application.dropping_series', 'false', true);
    END IF;
END;
$function$;