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Jacek, > Merge engine > ------------ > - Run test of merge engine to check if it be used instead > of subchunks. See: > https://dev.lsstcorp.org/trac/wiki/db/tests/MySql/MergeEngine2 > - conclusions: NOT good for subchunking I don't understand this. I thought the entire point was to use the individual subchunk tables for things like near neighbor, not the merged table, which would be used for all other types of queries. In that mode, the performance doesn't look too bad: mysql> select sum(ra_PS) from o0035; +------------------+ | sum(ra_PS) | +------------------+ | 1058.37348206197 | +------------------+ 1 row in set (0.02 sec) mysql> select sum(ra_PS) from merged; +------------------+ | sum(ra_PS) | +------------------+ | 109598266.899447 | +------------------+ 1 row in set (1.29 sec) The open files may or may not be a problem; having tens of thousands open is usually not an issue. -- Kian-Tat Lim, LSST Data Management, [log in to unmask] ######################################################################## Use REPLY-ALL to reply to list To unsubscribe from the QSERV-L list, click the following link: https://listserv.slac.stanford.edu/cgi-bin/wa?SUBED1=QSERV-L&A=1