what's changed: *) as advertised, i'm no longer bothering to cache invalid bits. hint bit i/o via rollbacked transactions is not a big deal IMNSHO, so they will work as they have always done. *) all the tuple visibility routines are now participating in the cache *) xmax commit bits are now being cached, not just xmin. this prevents hint bit i/o following deletes. *) juggled the cache interaction a bit so the changes to the visibility routines could be a lot more surgical. specifically, I reverted SetHintBits() to return void and put the cache adjustment inside 'SetHintBitsCache()' which sets the bits, dirties, and adjusts the cache. SetHintBitsNonDirty() only sets the bits without dirtying the page, and is called when you get a cache hit. *) various minor cleanups, decided to keep pageindex as type TransactionId since that's what clog does. *) made a proper init function, put cache data into CacheMemoryContext, and moved the cache data pointer references into the page structure
performance testing done: *) select only pgbench and standard i/o pgbech tests don't show performance difference within statistical noise. The test I need to do, a cache and clog thrashing test, I haven't found a clean way to put together yet. I'm really skeptical that any problems will show up there. That said, I am satisfied the patch does what it is supposed to do -- eliminates hint bit i/o without for cases where it is a big headache without penalizing other cases. Anyone that would like to comment on the technique or other points of the patch please do so (otherwise it's time for the 'fest). merlin
hbache_v6.patch
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