workload/tpcc: make uuid generation deterministic

[danhhz]

Also reduce allocations. Bonus: history table rows are now generated in
primary key order, which the new direct ingestion IMPORT in 19.2 will
take advantage of.

name                               old time/op    new time/op    delta
InitialData/tpcc/warehouses=1-8       385ms ± 1%     355ms ± 0%   -7.80%  (p=0.008 n=5+5)

name                               old speed      new speed      delta
InitialData/tpcc/warehouses=1-8     286MB/s ± 1%   310MB/s ± 0%   +8.45%  (p=0.008 n=5+5)

name                               old alloc/op   new alloc/op   delta
InitialData/tpcc/warehouses=1-8       914kB ± 0%     194kB ± 0%  -78.76%  (p=0.008 n=5+5)

name                               old allocs/op  new allocs/op  delta
InitialData/tpcc/warehouses=1-8       60.6k ± 0%      0.6k ± 0%  -99.02%  (p=0.008 n=5+5)

Release note: None

[cockroach-teamcity]

This change is 

[nvanbenschoten]

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @danhhz and @nvanbenschoten)

---

pkg/workload/tpcc/generate.go, line 61 at r1 (raw file):

	middleName = []byte(`OE`)
	goodCredit = []byte("GC")
	badCredit  = []byte("BC")

We can remove the cast where these are used now, right?

---

pkg/workload/tpcc/generate.go, line 436 at r1 (raw file):

Quoted 4 lines of code…

	// Then, because this involves some floats (and
	// who knows what kind of crazy rounding things can happen when floats are
	// involved), we make sure they're unique by sticking the original row index
	// in the lower 8 bytes.

Good idea!

[danhhz]

TFTR!

bors r=nvanbenschoten

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @danhhz and @nvanbenschoten)

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pkg/workload/tpcc/generate.go, line 61 at r1 (raw file):

Previously, nvanbenschoten (Nathan VanBenschoten) wrote…

We can remove the cast where these are used now, right?

already done. one of the two was being conditionally assigned to the credit variable, which lost its cast

[craig]

Build succeeded

• GitHub CI (Cockroach)