EvoBGP/docs/db-diagnostics.md

Диагностика схемы PostgreSQL (EvoBGP)

Runbook для оценки объёма БД и узких мест перед и после миграций оптимизации схемы. Выполнять на staging или production read-only сессией.

Подключение

psql "$EVOBGP_DATABASE_URL"

1. Размеры таблиц и индексов

SELECT relname,
       pg_size_pretty(pg_total_relation_size(relid)) AS total,
       pg_size_pretty(pg_relation_size(relid)) AS heap,
       pg_size_pretty(pg_indexes_size(relid)) AS indexes
FROM pg_catalog.pg_statio_user_tables
ORDER BY pg_total_relation_size(relid) DESC;

Ожидание: лидеры — revision_materialized_prefix, config_revision (TOAST от preview), JSONB-кэши.

2. Seq scan (горячие таблицы)

SELECT schemaname, relname, seq_scan, seq_tup_read, idx_scan
FROM pg_stat_user_tables
WHERE schemaname = 'public'
ORDER BY seq_tup_read DESC;

Сброс статистики после деплоя: SELECT pg_stat_reset(); (только осознанно, теряется baseline).

3. Неиспользуемые индексы

SELECT indexrelname, idx_scan, pg_size_pretty(pg_relation_size(indexrelid)) AS size
FROM pg_stat_user_indexes
WHERE schemaname = 'public' AND idx_scan = 0
ORDER BY pg_relation_size(indexrelid) DESC;

4. Дубликаты в materialized prefixes

Перед UNIQUE (revision_id, prefix, community_id, source):

SELECT revision_id, prefix, community_id, source, COUNT(*) AS n
FROM revision_materialized_prefix
GROUP BY 1, 2, 3, 4
HAVING COUNT(*) > 1
LIMIT 20;

5. Шаблон отчёта staging

Метрика	До	После	Дата
revision_materialized_prefix total
config_revision total
module_prefix_snapshot total
asn_prefix_cache total
Top seq_scan table
Unused indexes (count)

6. EXPLAIN для типовых запросов

-- Список префиксов ревизии (keyset)
EXPLAIN (ANALYZE, BUFFERS)
SELECT prefix::text, community_id::text, source
FROM revision_materialized_prefix
WHERE revision_id = '<revision-uuid>'::uuid
ORDER BY id
LIMIT 51;

-- Diff added (anti-join)
EXPLAIN (ANALYZE, BUFFERS)
SELECT b.prefix::text
FROM revision_materialized_prefix b
LEFT JOIN revision_materialized_prefix a
  ON a.revision_id = '<rev-a>'::uuid AND a.prefix = b.prefix
WHERE b.revision_id = '<rev-b>'::uuid
  AND a.prefix IS NULL
ORDER BY b.prefix
LIMIT 5001;

Цель: Index Scan / Bitmap Index Scan по (revision_id, …), без Seq Scan на больших таблицах.