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Index Compression worthit? |
Fri, Feb 19 2021 5:42 PM | Permanent Link |
David | I currently don't use any index compression and wondering if this is a mistake of mine and am I likely to see any performance improvement/degradation by using it.
I have a few text based fields that are not unique or primary eg 'TI-21.0001\SP-M.1234' that might have a couple of records linked to it, usually no more than 4 using that index key, otherwise they are all different but have a similar format, They are not all the same size(max 30 chars). I think in this case I would need to use Full compression. I am noticing the .idx files on some tables with ~37k records in it is larger than the dat file and I know compression would sort this, but just want other peoples opinion on using compression. Thanks David. |
Sun, Feb 21 2021 7:17 PM | Permanent Link |
Raul Team Elevate | On 2/19/2021 5:42 PM, David wrote:
> I currently don't use any index compression and wondering if this is a mistake of mine and am I likely to see any performance improvement/degradation by using it. > > I have a few text based fields that are not unique or primary eg 'TI-21.0001\SP-M.1234' that might have a couple of records linked to it, usually no more than 4 using that index key, otherwise they are all different but have a similar format, They are not all the same size(max 30 chars). I think in this case I would need to use Full compression. > > I am noticing the .idx files on some tables with ~37k records in it is larger than the dat file and I know compression would sort this, but just want other peoples opinion on using compression. IMHO index compression is a trade-off between reading/writing less data vs spending CPU cycles on compression. In theory it helps with caching (less info needed to cache in theory so might remain in cache longer). I suggest run some tests to see if it would make any difference both for performance and/or index table sizes (which alone might be worthwhile). Without knowing more full compression should be first choice to test if they are just string fields. Raul |
Mon, Feb 22 2021 11:16 AM | Permanent Link |
David | Thanks Raul.
I know the manual says there really is no good reason not to use index compressions and I suppose I should have paid more attention to this, I think the reduced index file size in itself might be helpful meaning less data to write to disk as my server has a slow RAID write on it. I normally stay away from compression for a fear that it might make things worse if something goes wrong as recovery is not quite so easy, but that was manly from file system compression, not in a DB. I have scouted around the forum and I have not see anything that indicates there being issues with using compression and I was just looking for an opinion of others who have used/not used it. Regards David. Raul wrote: On 2/19/2021 5:42 PM, David wrote: IMHO index compression is a trade-off between reading/writing less data vs spending CPU cycles on compression. In theory it helps with caching (less info needed to cache in theory so might remain in cache longer). I suggest run some tests to see if it would make any difference both for performance and/or index table sizes (which alone might be worthwhile). Without knowing more full compression should be first choice to test if they are just string fields. Raul |
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