Hello, We're using a statement like this to dump between 500K and >5 million rows. COPY(SELECT SomeID FROM SomeTable WHERE SomeColumn > '0') TO '/dev/shm/SomeFile.csv' Upon first run, this operation can take several minutes. Upon second run, it will be complete in generally well under a minute. Some observations/thoughts: -- When watching the file grow, it will "trickle" upon first run, increasing in size by only a few kb/s. Upon second run, it will grow by megabytes per second. -- If we dump to disk, the same behavior is observed - no apparent RAM contention issues. -- The SELECT by itself will complete typically in a few seconds, either on second or first run. -- Upon the first run, the PostgreSQL process typically consumes <10% CPU. -- In very rare cases, we've seen even the first run be as fast as the second run. -- There is no other activity on the server while performing these tests. -- SomeID is just an int -- CPU usage (wait %) is low; seems as though there is some other bottleneck Any thoughts on: -- tuning parameters to speed up the initial execution -- why is it so slow to begin with? -- possible areas to check for bottlenecks? -- better method for accomplishing the same thing? Thank you, H
