On 1/31/20 10:24 AM, Matthias Apitz wrote:
Hello, Since ages, we transfer data between different DBS (Informix, Sybase, Oracle, and now PostgreSQL) with our own written tool, based on Perl::DBI which produces a CSV like export in a common way, i.e. an export of Oracle can be loaded into Sybase and vice versa. Export and Import is done row by row, for some tables millions of rows. We produced a special version of the tool to export the rows into a format which understands the PostgreSQL's COPY command and got to know that the import into PostgreSQL of the same data with COPY is 50 times faster than with Perl::DBI, 2.5 minutes ./. 140 minutes for around 6 million rows into an empty table without indexes. How can COPY do this so fast?
Well for one thing COPY does everything in a single transaction, which is both good and bad. The good is that it is fast, the bad is that a single error will rollback the entire operation.
COPY also uses it's own method for transferring data. For all the details see:
https://www.postgresql.org/docs/12/protocol-flow.html#PROTOCOL-COPY
matthias
-- Adrian Klaver adrian.klaver@xxxxxxxxxxx
