* use []string for value string pointers: one allocation instead of
one per value.
* use one string for all key/value pairs, instead of one for each.
After this change, one Hstore will share two allocations: one string
and one []string. The disadvantage is that it cannot be deallocated
until all key/value pairs are unused. This means if an application
takes a single key or value from the Hstore and holds on to it, its
memory footprint will increase. I would guess this is an unlikely
problem, but it is possible.
The benchstat results from my M1 Max are below.
goos: darwin
goarch: arm64
pkg: github.com/jackc/pgx/v5/pgtype
│ orig.txt │ new.txt │
│ sec/op │ sec/op vs base │
HstoreScan/databasesql.Scan-10 82.11µ ± 1% 82.66µ ± 2% ~ (p=0.436 n=10)
HstoreScan/text-10 83.30µ ± 1% 84.24µ ± 3% ~ (p=0.165 n=10)
HstoreScan/binary-10 15.987µ ± 2% 7.459µ ± 6% -53.35% (p=0.000 n=10)
geomean 47.82µ 37.31µ -21.98%
│ orig.txt │ new.txt │
│ B/op │ B/op vs base │
HstoreScan/databasesql.Scan-10 56.23Ki ± 0% 56.23Ki ± 0% ~ (p=0.324 n=10)
HstoreScan/text-10 65.12Ki ± 0% 65.12Ki ± 0% ~ (p=0.675 n=10)
HstoreScan/binary-10 21.09Ki ± 0% 20.73Ki ± 0% -1.70% (p=0.000 n=10)
geomean 42.58Ki 42.34Ki -0.57%
│ orig.txt │ new.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-10 464.00 ± 0% 41.00 ± 0% -91.16% (p=0.000 n=10)
geomean 635.4 283.0 -55.46%
¹ all samples are equal
Evan Jones
2de94187f5