Directly store score as double in the dict of zset.

[RayaCoo]

In the past, we used void * for dict to store the score of elements in zset. This mean we had to dereference the score ervey time we accesse it. For example, *(double *)dictGetVal(de). This added extra dereference overhead, and for zunion[store] command, value of dict has been set twice. like this :

else if (op == SET_OP_UNION) {
    ...
    dictSetDoubleVal(de, score);
    ...
    dictSetVal(dstzset->dict, de, &znode->score);
    ...
}

Since double field has been add in dictEntry value union by commit, and for zset, the value stored in dict will always be double type, we can directly store score as double, which can improves the code's readability and reduces extra dereferencing overhead.

[codecov]

Codecov Report

Attention: Patch coverage is 96.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 70.56%. Comparing base (2d1eca5) to head (eb7cbc3).

Files with missing lines	Patch %	Lines
src/module.c	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable     #959      +/-   ##
============================================
+ Coverage     70.39%   70.56%   +0.16%     
============================================
  Files           114      114              
  Lines         61634    61643       +9     
============================================
+ Hits          43388    43499     +111     
+ Misses        18246    18144     -102     

Files with missing lines	Coverage Δ
src/aof.c	80.05% <100.00%> (ø)
src/db.c	88.41% <100.00%> (ø)
src/debug.c	53.67% <100.00%> (ø)
src/defrag.c	86.58% <100.00%> (+0.82%)	⬆️
src/geo.c	93.48% <100.00%> (+0.01%)	⬆️
src/rdb.c	75.43% <100.00%> (-0.88%)	⬇️
src/t_zset.c	95.52% <100.00%> (-0.13%)	⬇️
src/module.c	9.64% <0.00%> (ø)

... and 12 files with indirect coverage changes

[hpatro]

You don't need to introduce this new method and expose it. Rather you could do it in a pair of operation, create a dict entry and set the value.

dictAddRaw(...);
dictSetDoubleVal(...);

[RayaCoo]

Thanks for your advice, the dictSetDoubleVal function has been removed.

[hpatro]

@RayaCoo Could you run some benchmark around this to check if there is any performance gain?