Benchmark: What is the efficient way to import too many records?

NOTE: This memorandum is write about PostgreSQL.

I’m interested in the way for to import too many records efficiently. The COPY FROM query looks good to me.

I like the bulk INSERT query, because it easy to use. But the bulk INSERT query requires memory size to buffer records.

The COPY FROM query doesn’t require buffering records. The wrote records will buffer at PostgreSQL server. (May it cause I/O wait at PostgreSQL?)