sql: diagnose and fix very very slow splits in sql tests

[mberhault]

to reproduce: comment out the config.TestingDisableTableSplits lines in sql/logic_test.go
Also in sql/rename_test.go

[petermattis]

@mberhault Is this still happening? Is there anything to be done here?

[mberhault]

I'll have to check again. Originally, splits would make the sql logic tests incredibly slow since we were doing a lot DB and table creations. It may still be the case.

[tamird]

Visiting for triage. Applied this patch:

diff --git a/sql/logic_test.go b/sql/logic_test.go
index 890fbaf..b4bc2e4 100644
--- a/sql/logic_test.go
+++ b/sql/logic_test.go
@@ -38,7 +38,6 @@ import (
    "time"
    "unicode/utf8"

-   "github.com/cockroachdb/cockroach/config"
    "github.com/cockroachdb/cockroach/security"
    "github.com/cockroachdb/cockroach/server"
    "github.com/cockroachdb/cockroach/sql"
@@ -1047,10 +1046,6 @@ func (t *logicTest) traceStop() {
 func TestLogic(t *testing.T) {
    defer leaktest.AfterTest(t)()

-   // TODO(marc): splitting ranges at table boundaries causes
-   // a blocked task and won't drain. Investigate and fix.
-   defer config.TestingDisableTableSplits()()
-
    var globs []string
    if *bigtest {
        const logicTestPath = "../../sqllogictest"

Before:

$ make test PKG=./sql TESTS=Logic
go test -v  -i ./sql
go test  -run "Logic" -timeout 1m10s ./sql
ok      github.com/cockroachdb/cockroach/sql    11.297s

After:

$ make test PKG=./sql TESTS=Logic
go test -v  -i ./sql
go test  -run "Logic" -timeout 1m10s ./sql
ok      github.com/cockroachdb/cockroach/sql    16.482s

Looks like the original TODO no longer applies, but there's definitely a performance hit.