hard20 pts · first answer countspostgresqlindexingdeployment

Adding an index to a live big table

You need a new index on a 200-million-row PostgreSQL table that receives writes all day. Which statement is correct?

A.A plain CREATE INDEX takes no locks, so it is safe at any timeB.Wrap CREATE INDEX CONCURRENTLY in a BEGIN/COMMIT block so a failure rolls back cleanly instead of leaving a broken, half-built indexC.Use ALTER TABLE ... ADD INDEX ... ONLINE, which is PostgreSQL's non-blocking syntaxD.Use CREATE INDEX CONCURRENTLY: no write blocking, but slower, no transaction block, and it may leave an INVALID index

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