-- 087_fdw_server_options.sql
-- Issue #769 Part B (finding #13) — FDW server performance options.
--
-- Context:
--   SERVER gendesign_remote was created by 060_postgres_fdw_extension.sql.
--   The current options are: host, dbname, port, extensions, connect_timeout.
--   Two planning options are missing:
--     fetch_size        — rows fetched per round-trip (default 100, raise to 10000
--                         for bulk cursor-based pagination in import_rosreestr_dkp).
--     use_remote_estimate — let planner query ANALYZE stats from the remote server
--                         to produce accurate cost estimates for the 6.8M-row
--                         rosreestr_deals foreign table and quarter_price_index MV.
--
-- Idempotency:
--   ALTER SERVER ... OPTIONS (ADD ...) raises ERROR if the option already exists.
--   ALTER SERVER ... OPTIONS (SET ...) raises ERROR if the option does not exist yet.
--   Therefore a DO $$ block checks pg_foreign_server.srvoptions for each option:
--     - If present → SET (update the value in case it was previously set differently).
--     - If absent  → ADD (insert for the first time).
--   This is safe to run repeatedly regardless of prior state.
--
-- Dependencies:
--   060_postgres_fdw_extension.sql (gendesign_remote server must exist).
--
-- Deploy order:
--   Apply after 060_postgres_fdw_extension.sql. No FDW USER MAPPING changes required.
--   Effect is immediate — next FDW query uses the new planner options.

BEGIN;

DO $$
DECLARE
    v_opts text[];
BEGIN
    -- Read current srvoptions array for gendesign_remote.
    SELECT COALESCE(srvoptions, ARRAY[]::text[])
      INTO v_opts
      FROM pg_foreign_server
     WHERE srvname = 'gendesign_remote';

    IF NOT FOUND THEN
        RAISE EXCEPTION 'FDW server gendesign_remote not found — apply 060_postgres_fdw_extension.sql first';
    END IF;

    -- fetch_size: rows per FDW cursor round-trip (default 100 → 10000)
    IF v_opts @> ARRAY['fetch_size=10000'] THEN
        NULL; -- already correct value, no-op
    ELSIF EXISTS (
        SELECT 1 FROM unnest(v_opts) AS opt WHERE opt LIKE 'fetch_size=%'
    ) THEN
        ALTER SERVER gendesign_remote OPTIONS (SET fetch_size '10000');
    ELSE
        ALTER SERVER gendesign_remote OPTIONS (ADD fetch_size '10000');
    END IF;

    -- use_remote_estimate: push ANALYZE stats collection to remote for better plans
    IF v_opts @> ARRAY['use_remote_estimate=true'] THEN
        NULL; -- already correct value, no-op
    ELSIF EXISTS (
        SELECT 1 FROM unnest(v_opts) AS opt WHERE opt LIKE 'use_remote_estimate=%'
    ) THEN
        ALTER SERVER gendesign_remote OPTIONS (SET use_remote_estimate 'true');
    ELSE
        ALTER SERVER gendesign_remote OPTIONS (ADD use_remote_estimate 'true');
    END IF;
END
$$;

COMMIT;