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Tom Lane c64d0cd5ce 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.

Discussion: https://postgr.es/m/20190103163340.GA15803@britannica.bec.de
2019-01-09 19:47:46 -05:00
..
base64.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
config_info.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
controldata_utils.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
fe_memutils.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
file_perm.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
file_utils.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
int.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
int128.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
ip.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
keywords.h Replace the data structure used for keyword lookup. 2019-01-06 17:02:57 -05:00
kwlookup.h Use perfect hashing, instead of binary search, for keyword lookup. 2019-01-09 19:47:46 -05:00
link-canary.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
md5.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
pg_lzcompress.h Phase 2 of pgindent updates. 2017-06-21 15:19:25 -04:00
relpath.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
restricted_token.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
saslprep.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
scram-common.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
sha2.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
string.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
unicode_norm.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
unicode_norm_table.h Update copyright for 2019 2019-01-02 12:44:25 -05:00
username.h Update copyright for 2019 2019-01-02 12:44:25 -05:00