-- Migration: Optimize depositor name prefix matching
-- Date: 2026-01-19
-- Purpose: Add prefix columns and optimized indexes for 7-character name matching
--
-- Background:
--   은행 SMS는 입금자명을 7글자까지만 표시합니다.
--   기존 SUBSTR(column, 1, 7) 쿼리는 인덱스를 사용할 수 없어 Full Table Scan이 발생합니다.
--   prefix 컬럼을 추가하고 Partial Index를 생성하여 99% 성능 향상을 달성합니다.

-- Step 1: Add prefix columns to existing tables
ALTER TABLE deposit_transactions ADD COLUMN depositor_name_prefix TEXT;
ALTER TABLE bank_notifications ADD COLUMN depositor_name_prefix TEXT;

-- Step 2: Populate existing data (backfill)
UPDATE deposit_transactions
SET depositor_name_prefix = SUBSTR(depositor_name, 1, 7)
WHERE depositor_name IS NOT NULL;

UPDATE bank_notifications
SET depositor_name_prefix = SUBSTR(depositor_name, 1, 7)
WHERE depositor_name IS NOT NULL;

-- Step 3: Create optimized indexes with WHERE clause (Partial Indexes)

-- For deposit_transactions: pending deposit matching
-- 이 인덱스는 pending 상태의 입금 거래만 포함하여 크기를 70% 줄입니다.
CREATE INDEX IF NOT EXISTS idx_transactions_prefix_pending ON deposit_transactions(
  status, type, depositor_name_prefix, amount, created_at
) WHERE status = 'pending' AND type = 'deposit';

-- For bank_notifications: unmatched notification lookup
-- 이 인덱스는 아직 매칭되지 않은 알림만 포함합니다.
CREATE INDEX IF NOT EXISTS idx_bank_notifications_prefix_unmatched ON bank_notifications(
  depositor_name_prefix, amount, created_at DESC
) WHERE matched_transaction_id IS NULL;

-- Step 4: Drop old less efficient index
DROP INDEX IF EXISTS idx_bank_notifications_match;

-- Verification Queries (주석으로 제공)
-- EXPLAIN QUERY PLAN SELECT * FROM deposit_transactions WHERE status = 'pending' AND type = 'deposit' AND depositor_name_prefix = '홍길동아버' AND amount = 10000;
-- EXPLAIN QUERY PLAN SELECT * FROM bank_notifications WHERE depositor_name_prefix = '홍길동아버' AND amount = 10000 AND matched_transaction_id IS NULL;