Add DELETE query support

[benbjohnson]

Overview

This commit adds query language support for deleting series with a DELETE query.

Fixes #1647

/cc @jwilder

Required for all non-trivial PRs

• Rebased/mergable
• Tests pass
• CHANGELOG.md updated
• Sign CLA (if not already signed)

Required only if applicable

• InfluxQL Spec updated

[toni-moreno]

+1

[jwilder]

This will skip the c.size decrement below. Should add a c.size -= uint64(origSize) before continue

[benbjohnson]

Fixed in 2cf25a1.

[jwilder]

Needs a CHANGELOG update.

[benbjohnson]

@jwilder I forgot to push the CHANGELOG update. Fixed and pushed up.

[jwilder]

👍

[beckettsean]

OMGYES!

@benbjohnson any initial thoughts on how performant this is? Is it something a user could run during normal operations or would it be advisable only against a quiescent database?

What's the difference between DELETE SERIES cpu vs. DROP SERIES cpu, neither with WHERE conditions. In the first case the series is still in the index and in the second it's not?

[benbjohnson]

@beckettsean I'm not sure. @jwilder did the tsm1 implementation. He could probably speak on the performance characteristics.

[jwilder]

@beckettsean I'm still testing performance. Should work like drop series.

The difference between DELETE SERIES and DROP SERIES is that DELETE SERIES does not remove the series from the index so SHOW SERIES will still list it even if you deleted all data.

This behavior is a little odd after playing with this because, if you restart the server, the series are gone. @pauldix is there reason why DELETE SERIES should not remove the series from the index if the series data is fully removed?

[nemesifier]

Thanks for adding this.