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were discussed last year, but we felt it was too late in the 8.3 cycle to change the code immediately. Specifically, the patch: * Reduces the minimum datum size to be considered for compression from 256 to 32 bytes, as suggested by Greg Stark. * Increases the required compression rate for compressed storage from 20% to 25%, again per Greg's suggestion. * Replaces force_input_size (size above which compression is forced) with a maximum size to be considered for compression. It was agreed that allowing large inputs to escape the minimum-compression-rate requirement was not bright, and that indeed we'd rather have a knob that acted in the other direction. I set this value to 1MB for the moment, but it could use some performance studies to tune it. * Adds an early-failure path to the compressor as suggested by Jan: if it's been unable to find even one compressible substring in the first 1KB (parameterizable), assume we're looking at incompressible input and give up. (Possibly this logic can be improved, but I'll commit it as-is for now.) * Improves the toasting heuristics so that when we have very large fields with attstorage 'x' or 'e', we will push those out to toast storage before considering inline compression of shorter fields. This also responds to a suggestion of Greg's, though my original proposal for a solution was a bit off base because it didn't fix the problem for large 'e' fields. There was some discussion in the earlier threads of exposing some of the compression knobs to users, perhaps even on a per-column basis. I have not done anything about that here. It seems to me that if we are changing around the parameters, we'd better get some experience and be sure we are happy with the design before we set things in stone by providing user-visible knobs. |
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| .. | ||
| acl.h | ||
| array.h | ||
| ascii.h | ||
| builtins.h | ||
| cash.h | ||
| catcache.h | ||
| combocid.h | ||
| date.h | ||
| datetime.h | ||
| datum.h | ||
| dynahash.h | ||
| dynamic_loader.h | ||
| elog.h | ||
| errcodes.h | ||
| flatfiles.h | ||
| fmgrtab.h | ||
| formatting.h | ||
| geo_decls.h | ||
| guc_tables.h | ||
| guc.h | ||
| help_config.h | ||
| hsearch.h | ||
| inet.h | ||
| int8.h | ||
| inval.h | ||
| logtape.h | ||
| lsyscache.h | ||
| memutils.h | ||
| nabstime.h | ||
| numeric.h | ||
| palloc.h | ||
| pg_crc.h | ||
| pg_locale.h | ||
| pg_lzcompress.h | ||
| pg_rusage.h | ||
| plancache.h | ||
| portal.h | ||
| ps_status.h | ||
| rel.h | ||
| relcache.h | ||
| resowner.h | ||
| selfuncs.h | ||
| syscache.h | ||
| timestamp.h | ||
| tqual.h | ||
| tuplesort.h | ||
| tuplestore.h | ||
| typcache.h | ||
| tzparser.h | ||
| uuid.h | ||
| varbit.h | ||
| xml.h | ||