Optimize HRANDFIELD and ZRANDMEMBER case 4 when ziplist encoded #8444
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sundb
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Feb 4, 2021
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It is inefficient to repeatedly pick a single random element from a ziplist. For CASE4, which is when the user requested a low number of unique random picks from the collectoin, we used thta pattern. Now we use a different algorithm that picks unique elements from a ziplist, and guarentee no duplicate but doesn't provide random order (which is only needed in the non-unique random picks case) Co-authored-by: xinluton <xinluton@qq.com>
yossigo
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Feb 7, 2021
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JackieXie168
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Mar 2, 2021
…s#8444) It is inefficient to repeatedly pick a single random element from a ziplist. For CASE4, which is when the user requested a low number of unique random picks from the collectoin, we used thta pattern. Now we use a different algorithm that picks unique elements from a ziplist, and guarentee no duplicate but doesn't provide random order (which is only needed in the non-unique random picks case) Unrelated changes: * change ziplist count and indexes variables to unsigned * solve compilation warnings about uninitialized vars in gcc 10.2 Co-authored-by: xinluton <xinluton@qq.com>
oranagra
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May 22, 2023
) Optimized HRANDFIELD and ZRANDMEMBER commands as in #8444, CASE 3 under listpack encoding. Boost optimization to CASE 2.5. CASE 2.5 listpack only. Sampling unique elements, in non-random order. Listpack encoded hashes / zsets are meant to be relatively small, so HRANDFIELD_SUB_STRATEGY_MUL / ZRANDMEMBER_SUB_STRATEGY_MUL isn't necessary and we rather not make copies of the entries. Instead, we emit them directly to the output buffer. Simple benchmarks shows it provides some 400% improvement in HRANDFIELD and ZRANGESTORE both in CASE 3. Unrelated changes: remove useless setTypeRandomElements and fix a typo.
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It is inefficient to repeatedly pick a single random element from a
ziplist.
For CASE4, which is when the user requested a low number of unique
random picks from the collectoin, we used thta pattern.
Now we use a different algorithm that picks unique elements from a
ziplist, and guarentee no duplicate but doesn't provide random order
(which is only needed in the non-unique random picks case)
Unrelated changes:
Co-authored-by: xinluton xinluton@qq.com