83bed06be4
Add a validity flag to DCHCacheEntry and NUMCacheEntry entries, and do not set it true until after we've parsed the supplied format string. This allows dealing with possible errors while parsing the format without the baroque hack that was there before (which only covered errors within NUMDesc_prepare, anyway). We can get rid of the PG_TRY in NUMDesc_prepare, as well as last_NUMCacheEntry and NUM_cache_remove. (Essentially, this reverts commit ff783fbae in favor of a less fragile solution; the problems with that approach are well illustrated by later hacking such as 55f927a46.) In passing, define the size of these caches as DCH_CACHE_ENTRIES not DCH_CACHE_FIELDS + 1 (whoever thought that was a good definition?) and likewise for the NUM cache. Also const-ify format string parameters where convenient, and merge duplicated cache lookup logic. This is primarily driven by a proposed patch from Artur Zakirov, which introduced some ereport's into format string parsing for the datetime case. He proposed preventing the creation of invalid cache entries by parsing the format string first into a local-variable array, and then copying that to a cache entry. That seemed a bit ugly to me, and anyway randomly different from the way the identical problem had been solved for the numeric case. Let's make the two sets of code more similar not less so. I'm not sure whether we'll adopt the new error conditions Artur proposes, but this patch seems like good code cleanup and future-proofing in any case. The existing code is critically (and undocumented-ly) dependent on no elog being thrown out of several nontrivial functions, which is trouble waiting to happen, though it doesn't seem to be actively broken today. Discussion: <b2a39359-3282-b402-f4a3-057aae500ee7@postgrespro.ru>
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