Medium Database Administrator questions

34 questions · 10 points each for a correct first answer.

1. 1.Composite index column orderindexing, query-tuningmedium
2. 2.Reading an EXPLAIN ANALYZE planquery-tuning, postgresqlmedium
3. 3.Non-repeatable readtransactions, isolation-levelsmedium
4. 4.Why PostgreSQL needs VACUUMpostgresql, mvccmedium
5. 5.What PITR needsbackup-recovery, postgresqlmedium
6. 6.Risk of asynchronous replicationreplication, high-availabilitymedium
7. 7.Why use a connection poolerconnection-pooling, postgresqlmedium
8. 8.Covering indexindexing, postgresqlmedium
9. 9.Slow deep paginationquery-tuning, indexingmedium
10. 10.Which query to tune firstquery-tuning, postgresqlmedium
11. 11.NOT IN returns nothingsqlmedium
12. 12.UNIQUE column with NULLspostgresql, data-modellingmedium
13. 13.Adding an index on a live tableindexing, postgresqlmedium
14. 14.Sort Method: external mergequery-tuning, postgresqlmedium
15. 15.Bad plan right after a bulk loadquery-tuning, postgresqlmedium
16. 16.Sizing shared_bufferspostgresql, performancemedium
17. 17.Session state behind pgBouncerconnection-pooling, postgresqlmedium
18. 18.Workers fighting over jobslocking, postgresqlmedium
19. 19.MySQL default isolation levelmysql, isolation-levelsmedium
20. 20.Measuring replica lagreplication, monitoringmedium
21. 21.Reports cancelled on the replicareplication, postgresqlmedium
22. 22.Is pg_dump consistent?backup-recovery, postgresqlmedium
23. 23.Restoring a Percona XtraBackupbackup-recovery, mysqlmedium
24. 24.Deleting a customer takes secondsindexing, data-modellingmedium
25. 25.Disk not freed after a big deletepostgresql, mvccmedium
26. 26.Bloat from an idle sessionpostgresql, mvccmedium
27. 27.A migration froze the whole applocking, postgresqlmedium
28. 28.Indexing only pending rowsindexing, postgresqlmedium
29. 29.Searching inside textindexing, postgresqlmedium
30. 30.Fast JSONB filtersindexing, postgresqlmedium
31. 31.Row vs statement binlog formatmysql, replicationmedium
32. 32.Multi-AZ vs read replica on RDShigh-availability, replicationmedium
33. 33.Terraform plan wants to replace the DBautomation, high-availabilitymedium
34. 34.Counting a huge table quicklyquery-tuning, postgresqlmedium