Cache overlapping blocks #2239
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Cache overlapping blocks #2239
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…ssing. Signed-off-by: Cyril Tovena <cyril.tovena@gmail.com>
Signed-off-by: Cyril Tovena <cyril.tovena@gmail.com>
Signed-off-by: Cyril Tovena <cyril.tovena@gmail.com>
Codecov Report
@@ Coverage Diff @@
## master #2239 +/- ##
==========================================
+ Coverage 62.07% 62.27% +0.19%
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Files 156 157 +1
Lines 12531 12650 +119
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+ Hits 7779 7878 +99
- Misses 4145 4161 +16
- Partials 607 611 +4
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owen-d
reviewed
Jun 19, 2020
| for _, b := range blocks { | ||
| // if we have already processed and cache block let's use it. | ||
| if cache, ok := c.overlappingBlocks[b.Offset()]; ok { | ||
| clone := *cache |
owen-d
approved these changes
Jun 19, 2020
slim-bean
reviewed
Jun 19, 2020
| blocks = append(blocks, b) | ||
| } | ||
| } | ||
| return blocks |
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could we gain anything by slicing up the existing c.blocks instead of allocating a new slice? Also curious if c.blocks was a slice of pointers if we could save a copy of the block here?
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I’ll check if it does help. There’s other place where I don’t reslice intentionally because reslicing keep underlying references.
slim-bean
approved these changes
Jun 19, 2020
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We (@slim-bean and I) realized that the batchIterator in Loki may re-process the same data over and over when more chunks are overlapping than the batch size. The side effect is that some users may process 30GIB of logs when in fact the real data is just 300MB. This affects a lot of queries.
This PR introduces a caches for block that are overlapping to avoid the costly decompression if we need to re-use a block when it overlaps with the next chunk. This is required for correctly deduping.
I've made a benchmark and run it before and after:
I've also run this in our ops cluster and realize a 25% speed up for filter queries.