Deflake DBBlockCacheTest1.WarmCacheWithBlocksDuringFlush

[ajkr]

Previously, automatic compaction could be triggered prior to the test invoking CompactRange(). It could lead to the following flaky failure:

/root/project/db/db_block_cache_test.cc:753: Failure
Expected equality of these values:
  1 + kNumBlocks
    Which is: 11
  options.statistics->getTickerCount(BLOCK_CACHE_INDEX_ADD)
    Which is: 10

A sequence leading to this failure was:

• Automatic compaction
  • files [1] [2] trivially moved
  • files [3] [4] [5] [6] trivially moved
• CompactRange()
  • files [7] [8] [9] trivially moved
  • file [10] trivially moved

In such a case, the index/filter block adds that the test expected did not happen since there were no new files.

This PR just tweaks settings to ensure the CompactRange() produces one new file.

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[cbi42]

LGTM thanks.

Curious what's causing CompactRange() to do or not do trivial move in this case? The files are all non-overlapping whether there's automatic compaction or not.

[ajkr]

Thanks for the review! If CompactRange() picked [7] [8] [9] [10] it would overlap [2] .. [6] on L1, because it's using std::to_string() which does not do zero padding so [10] gets ordered between [1] and [2].