On Wed, Jan 9, 2019 at 7:48 PM Tom Lane <t...@sss.pgh.pa.us> wrote: > Use perfect hashing, instead of binary search, for keyword lookup. > > We've been speculating for a long time that hash-based keyword lookup > ought to be faster than binary search, but up to now we hadn't found > a suitable tool for generating the hash function. Joerg Sonnenberger > provided the inspiration, and sample code, to show us that rolling our > own generator wasn't a ridiculous idea. Hence, do that. > > The method used here requires a lookup table of approximately 4 bytes > per keyword, but that's less than what we saved in the predecessor commit > afb0d0712, so it's not a big problem. The time savings is indeed > significant: preliminary testing suggests that the total time for raw > parsing (flex + bison phases) drops by ~20%. > > Patch by me, but it owes its existence to Joerg Sonnenberger; > thanks also to John Naylor for review.
Wow. That is a VERY significant improvement. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
