Redesign get_attstatsslot()/free_attstatsslot() for more safety and speed. The mess cleaned up in commit da0759600 is clear evidence that it's a bug hazard to expect the caller of get_attstatsslot()/free_attstatsslot() to provide the correct type OID for the array elements in the slot. Moreover, we weren't even getting any performance benefit from that, since get_attstatsslot() was extracting the real type OID from the array anyway. So we ought to get rid of that requirement; indeed, it would make more sense for get_attstatsslot() to pass back the type OID it found, in case the caller isn't sure what to expect, which is likely in binary- compatible-operator cases.
Another problem with the current implementation is that if the stats array element type is pass-by-reference, we incur a palloc/memcpy/pfree cycle for each element. That seemed acceptable when the code was written because we were targeting O(10) array sizes --- but these days, stats arrays are almost always bigger than that, sometimes much bigger. We can save a significant number of cycles by doing one palloc/memcpy/pfree of the whole array. Indeed, in the now-probably-common case where the array is toasted, that happens anyway so this method is basically free. (Note: although the catcache code will inline any out-of-line toasted values, it doesn't decompress them. At the other end of the size range, it doesn't expand short-header datums either. In either case, DatumGetArrayTypeP would have to make a copy. We do end up using an extra array copy step if the element type is pass-by-value and the array length is neither small enough for a short header nor large enough to have suffered compression. But that seems like a very acceptable price for winning in pass-by-ref cases.) Hence, redesign to take these insights into account. While at it, convert to an API in which we fill a struct rather than passing a bunch of pointers to individual output arguments. That will make it less painful if we ever want further expansion of what get_attstatsslot can pass back. It's certainly arguable that this is new development and not something to push post-feature-freeze. However, I view it as primarily bug-proofing and therefore something that's better to have sooner not later. Since we aren't quite at beta phase yet, let's put it in. Discussion: https://postgr.es/m/16364.1494520...@sss.pgh.pa.us Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/9aab83fc5039d83e84144b7bed3fb1d62a74ae78 Modified Files -------------- contrib/intarray/_int_selfuncs.c | 31 +- src/backend/executor/nodeHash.c | 25 +- src/backend/tsearch/ts_selfuncs.c | 18 +- src/backend/utils/adt/array_selfuncs.c | 85 ++---- src/backend/utils/adt/network_selfuncs.c | 214 ++++++-------- src/backend/utils/adt/rangetypes_selfuncs.c | 58 ++-- src/backend/utils/adt/selfuncs.c | 419 +++++++++++----------------- src/backend/utils/cache/lsyscache.c | 149 +++++----- src/include/utils/lsyscache.h | 34 ++- src/include/utils/selfuncs.h | 4 +- 10 files changed, 436 insertions(+), 601 deletions(-) -- Sent via pgsql-committers mailing list (pgsql-committers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-committers
