sql/randgen: avoid invalid inverted indexes in CREATE TABLE

[fqazi]

Previously, the create table made via the randgen component
could create invalid CREATE TABLE statements where the last
columns of an inverted index were descending. This could
lead to unexpected failures in certain workloads, which
expected valid statements from this components. To address
this, this patch stops randgen from generating CREATE table
statements with invalid inverted indexes.

Release note: None

[cockroach-teamcity]

This change is 

[fqazi]

This eliminates one workload-related failure at least in the randomized schema changer workload, and probably helps out others too.

[ajwerner]

Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @ajwerner and @fqazi)

---

pkg/sql/randgen/schema.go line 175 at r1 (raw file):

	nIdxs := rng.Intn(10)
	for i := 0; i < nIdxs; i++ {
		indexDef, ok := randIndexTableDefFromCols(rng, columnDefs, tableName, false /* isPrimaryIndex */, isMultiRegion)

Should we instead change this function to not set the direction illegally if it chooses to create an inverted index?

[fqazi]

Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @ajwerner)

---

pkg/sql/randgen/schema.go line 175 at r1 (raw file):

Previously, ajwerner wrote…

Should we instead change this function to not set the direction illegally if it chooses to create an inverted index?

Good point, changed this to fix the generator instead of skipping over them.

[ajwerner]

Reviewed 1 of 1 files at r2, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @fqazi)

[fqazi]

@ajwerner TFTR!

[fqazi]

bors r+

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)