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remove the single backing string optimization 

This is a bit slower than using this optimization, but ensures this
version does not change garbage collection behavior. This does still
using a single []string for all the *string value pointers because
that is what text parsing already does. This makes the two behave
similarly.

benchstat results of master versus this version:

                               │  orig.txt   │   new-binary-no-share-string.txt    │
                               │   sec/op    │   sec/op     vs base                │
HstoreScan/databasesql.Scan-10   82.11µ ± 1%   81.71µ ± 2%        ~ (p=0.280 n=10)
HstoreScan/text-10               83.30µ ± 1%   82.45µ ± 1%   -1.02% (p=0.000 n=10)
HstoreScan/binary-10             15.99µ ± 2%   10.12µ ± 1%  -36.67% (p=0.000 n=10)
geomean                          47.82µ        40.86µ       -14.56%

                               │   orig.txt   │   new-binary-no-share-string.txt    │
                               │     B/op     │     B/op      vs base               │
HstoreScan/databasesql.Scan-10   56.23Ki ± 0%   56.23Ki ± 0%       ~ (p=0.128 n=10)
HstoreScan/text-10               65.12Ki ± 0%   65.12Ki ± 0%       ~ (p=0.541 n=10)
HstoreScan/binary-10             21.09Ki ± 0%   19.87Ki ± 0%  -5.75% (p=0.000 n=10)
geomean                          42.58Ki        41.75Ki       -1.95%

                               │  orig.txt  │    new-binary-no-share-string.txt    │
                               │ allocs/op  │ allocs/op   vs base                  │
HstoreScan/databasesql.Scan-10   744.0 ± 0%   744.0 ± 0%        ~ (p=1.000 n=10) ¹
HstoreScan/text-10               743.0 ± 0%   743.0 ± 0%        ~ (p=1.000 n=10) ¹
HstoreScan/binary-10             464.0 ± 0%   316.0 ± 0%  -31.90% (p=0.000 n=10)
geomean                          635.4        559.0       -12.02%
¹ all samples are equal

benchstat results of the version with one string and this version:

                               │ new-binary-share-everything.txt │    new-binary-no-share-string.txt    │
                               │             sec/op              │    sec/op     vs base                │
HstoreScan/databasesql.Scan-10                       81.80µ ± 1%    81.71µ ± 2%        ~ (p=1.000 n=10)
HstoreScan/text-10                                   82.77µ ± 1%    82.45µ ± 1%        ~ (p=0.063 n=10)
HstoreScan/binary-10                                 7.330µ ± 2%   10.124µ ± 1%  +38.13% (p=0.000 n=10)
geomean                                              36.75µ         40.86µ       +11.18%

                               │ new-binary-share-everything.txt │   new-binary-no-share-string.txt    │
                               │              B/op               │     B/op      vs base               │
HstoreScan/databasesql.Scan-10                      56.23Ki ± 0%   56.23Ki ± 0%       ~ (p=0.232 n=10)
HstoreScan/text-10                                  65.12Ki ± 0%   65.12Ki ± 0%       ~ (p=0.218 n=10)
HstoreScan/binary-10                                20.73Ki ± 0%   19.87Ki ± 0%  -4.11% (p=0.000 n=10)
geomean                                             42.34Ki        41.75Ki       -1.39%

                               │ new-binary-share-everything.txt │     new-binary-no-share-string.txt     │
                               │            allocs/op            │  allocs/op   vs base                   │
HstoreScan/databasesql.Scan-10                        744.0 ± 0%    744.0 ± 0%         ~ (p=1.000 n=10) ¹
HstoreScan/text-10                                    743.0 ± 0%    743.0 ± 0%         ~ (p=1.000 n=10) ¹
HstoreScan/binary-10                                  41.00 ± 0%   316.00 ± 0%  +670.73% (p=0.000 n=10)
geomean                                               283.0         559.0        +97.53%
¹ all samples are equal
pull/1648/head
Evan Jones 2023-06-16 15:50:45 -04:00 committed by Jack Christensen
parent 2de94187f5
commit bc8b1ca320
1 changed files with 3 additions and 5 deletions
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8
pgtype/hstore.go
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@ -191,10 +191,8 @@ func (scanPlanBinaryHstoreToHstoreScanner) Scan(src []byte, dst any) error {
rp += uint32Len
hstore := make(Hstore, pairCount)
// one allocation for all strings, rather than one per string
// one allocation for all *string, rather than one per string, just like text parsing
valueStrings := make([]string, pairCount)
// one shared string for all key/value strings
keyValueString := string(src[rp:])
for i := 0; i < pairCount; i++ {
if len(src[rp:]) < uint32Len {
@ -206,7 +204,7 @@ func (scanPlanBinaryHstoreToHstoreScanner) Scan(src []byte, dst any) error {
if len(src[rp:]) < keyLen {
return fmt.Errorf("hstore incomplete %v", src)
}
key := string(keyValueString[rp-uint32Len : rp-uint32Len+keyLen])
key := string(src[rp : rp+keyLen])
rp += keyLen
if len(src[rp:]) < uint32Len {
@ -216,7 +214,7 @@ func (scanPlanBinaryHstoreToHstoreScanner) Scan(src []byte, dst any) error {
rp += 4
if valueLen >= 0 {
valueStrings[i] = string(keyValueString[rp-uint32Len : rp-uint32Len+valueLen])
valueStrings[i] = string(src[rp : rp+valueLen])
rp += valueLen
hstore[key] = &valueStrings[i]