ALTER TABLE tb_payment
    ADD COLUMN merchant_identity varchar(100);

CREATE INDEX idx_payment_merchant_reconciliation
    ON tb_payment (payment_method, merchant_identity, paid_at, id)
    WHERE deleted_at IS NULL AND merchant_identity IS NOT NULL AND merchant_identity <> '';

COMMENT ON COLUMN tb_payment.merchant_identity IS '创建支付单时的收款身份快照：微信商户号或支付宝应用ID';