Hang in Intersect Scan

Install  6.6.1-9213

Install travel-sample

CREATE INDEX `def_type` ON `travel-sample`(`type`);  -- Already there

CREATE INDEX `ix10` ON `travel-sample`(`country`);

CREATE INDEX `ix11` ON `travel-sample`(`id`);

\set -timeout "1ms";

select type, country, x FROM `travel-sample` where type = "airline" AND country = "United States" and id = "abc";

repeat select statement many/many times at some point you will see hang.

Check go routine dump and you similar like below.

goroutine 7624472 [semacquire, 3633 minutes]:

sync.runtime_Semacquire(0xc00cf609ac)

        /home/couchbase/.cbdepscache/exploded/x86_64/go-1.11.4/go/src/runtime/sema.go:56 +0x39

sync.(*WaitGroup).Wait(0xc00cf609ac)

        /home/couchbase/.cbdepscache/exploded/x86_64/go-1.11.4/go/src/sync/waitgroup.go:130 +0x64

github.com/couchbase/query/execution.(*valueExchange).retrieveChildNoStop(0xc00cf60900, 0xc00cf606c0)

        /home/couchbase/jenkins/workspace/couchbase-server-unix/goproj/src/github.com/couchbase/query/execution/exchange.go:428 +0x85

github.com/couchbase/query/execution.(*base).childrenWaitNoStop(0xc00cf60900, 0xc004a69e00, 0x2, 0x10)

        /home/couchbase/jenkins/workspace/couchbase-server-unix/goproj/src/github.com/couchbase/query/execution/base.go:741 +0x1c7

github.com/couchbase/query/execution.(*IntersectScan).RunOnce.func1()

        /home/couchbase/jenkins/workspace/couchbase-server-unix/goproj/src/github.com/couchbase/query/execution/scan_intersect.go:146 +0x7f6

github.com/couchbase/query/util.(*Once).Do(0xc00cf60a08, 0xc0047a6f88)

        /home/couchbase/jenkins/workspace/couchbase-server-unix/goproj/src/github.com/couchbase/query/util/sync.go:54 +0x4a

github.com/couchbase/query/execution.(*IntersectScan).RunOnce(0xc00cf60900, 0xc006625b00, 0x0, 0x0)

        /home/couchbase/jenkins/workspace/couchbase-server-unix/goproj/src/github.com/couchbase/query/execution/scan_intersect.go:61 +0x82

created by github.com/couchbase/query/execution.(*base).runConsumer.func1

        /home/couchbase/jenkins/workspace/couchbase-server-unix/goproj/src/github.com/couchbase/query/execution/base.go:805 +0x2d6