b9dc6ad7ab
When all table blocks were removed from the query cache the client session
hung in a tight loop waiting on an impossible condition while consuming a lot
of CPU.
This patch also corrects an error which caused valid tables to sometimes be
removed from the query cache.
mysql-test/r/query_cache.result:
Added test case to make sure server doesn't hang in a tight loop if last
table block is removed from the cache.
mysql-test/t/query_cache.test:
Added test case to make sure server doesn't hang in a tight loop if last
table block is removed from the cache.
sql/sql_cache.cc:
- Refactored loop over table blocks. The invalidate_table() function effects
the elements over which we iterate. The previous stop condition was broken
due to a compiler optimization error probably caused by the goto-statement
pointing out of the loop. The effect being that tables_blocks was never
checked for null values and thus the loop never terminated.
- The new implementation uses two while loops instead of a goto-statement.
The tables_blocks is a circular list which becomes null if the last table
block is removed from the list.
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