On Dec 30, 2017, at 14:07, Brad Jorsch (Anomie) <bjorsch@wikimedia.org> wrote:

On Sat, Dec 30, 2017 at 1:07 PM, John <phoenixoverride@gmail.com> wrote:

Use the logging_userindex table instead of logging

That won't make much difference, since the select on the logging table isn't targeting any user columns.

On Sat, Dec 30, 2017 at 1:09 PM, John <phoenixoverride@gmail.com> wrote:

I would also find the first log of 2017 and use that instead of the timestamp

That would make it worse, since there's no index on (log_type, log_id). It'll either have to use the primary key and filter out all rows with a different log_type, or use one of the indexes that begins with log_type and filter out all the rows with an earlier log_id.

On Sat, Dec 30, 2017 at 1:32 PM, Dennis Tobar <dennis.tobar@gmail.com> wrote:

Replace count(*) with count(1) in the subquery. It could help (?) to improve the performance.

"count(*)" and "count(1)" should be treated equivalently. The "*" in "count(*)" does not cause the database to fetch all fields.

If anything, "count(*)" might be ever so slightly faster since it's literally staying "count the number of rows" rather than "count the number of rows where the constant 1 is not null". But the DB probably optimizes counting of a constant to make them identical.

--

Brad Jorsch (Anomie)
Senior Software Engineer
Wikimedia Foundation

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