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Lua: Use all characters to calculate string hash (#9449)

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For a lot of long strings which have same prefix which extends beyond
hashing limit, there will be many hash collisions which result in
performance degradation using commands like KEYS
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Kamil Cudnik 2021-09-09 11:47:26 +02:00 committed by GitHub
parent c50af0aeba
commit 7f88923b40
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1 changed files with 1 additions and 1 deletions
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2
deps/lua/src/lstring.c vendored
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@ -75,7 +75,7 @@ static TString *newlstr (lua_State *L, const char *str, size_t l,
TString *luaS_newlstr (lua_State *L, const char *str, size_t l) {
GCObject *o;
unsigned int h = cast(unsigned int, l); /* seed */
size_t step = (l>>5)+1; /* if string is too long, don't hash all its chars */
size_t step = 1;
size_t l1;
for (l1=l; l1>=step; l1-=step) /* compute hash */
h = h ^ ((h<<5)+(h>>2)+cast(unsigned char, str[l1-1]));