Avi Kivity a77bb1fe34 Merge "row_cache: Fix violation of continuity on concurrent eviction and population" from Tomasz ...

"
The problem happens under the following circumstances:

  - we have a partially populated partition in cache, with a gap in the middle

  - a read with no clustering restrictions trying to populate that gap

  - eviction of the entry for the lower bound of the gap concurrent with population

The population may incorrectly mark the range before the gap as continuous.
This may result in temporary loss of writes in that clustering range. The
problem heals by clearing cache.

Caught by row_cache_test::test_concurrent_reads_and_eviction, which has been
failing sporadically.

The problem is in ensure_population_lower_bound(), which returns true if
current clustering range covers all rows, which means that the populator has a
right to set continuity flag to true on the row it inserts. This is correct
only if the current population range actually starts since before all
clustering rows. Otherwise, we're populating since _last_row and should
consult it.

Fixes #3608.
"

* 'tgrabiec/fix-violation-of-continuity-on-concurrent-read-and-eviction' of github.com:tgrabiec/scylla:
  row_cache: Fix violation of continuity on concurrent eviction and population
  position_in_partition: Introduce is_before_all_clustered_rows()

(cherry picked from commit 31151cadd4)

2018-07-18 12:05:51 +02:00

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