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Help: why the LF index size increased so big?

hi guys,

I got a issue, that a LF typed index increased so big.

I have a table with a TIME column to store HH:mm:ss, and in fact, the value for this column is aligned with 5 minute (only 00:00:00, 00:05:00, 00:10:00, etc. will be saved in this column). thus, there are ONLY 288 unique values. and I use LF typed index.

there are about 15 billion data in this table, and if rebuild the LF index, the size will be ~24G. but after the new data inserted, the size of this LF index will increased so much. I got 200G after some days. and when delete and rebuild this index, i return to ~24G.

what's happens? and how to prevent this happen?

PS: I use IQ 16.0 SP8.

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  • Posted on Jul 06, 2016 at 10:50 AM

    With IQ 16, you should be using the HG index instead of LF. Size and performance should be better with an HG on lower cardinality columns. This is a change since IQ 15, but one that has proven to work quite well. Can you try with an HG and see how this behavior changes?

    Mark

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