Explain hangs sometimes because sample query does not return

Here is a very simple repro!

select 1, count (*) from T;

Looking at the related operator tree that feeds the sampling query, there are two datasourceScanOperators (one for T and one for the sample of T). There should only the sample data source. So the query seems malformed/

Here is the query

select 001, count(1) from R, S, T where  int64_default_null (R.u256) =  int64_default_null (S.u256)  and R.rand <= 1   and S.rand <= 1;

This happens only with CBO as samples are required.

The routine that hangs is

AnalysisUtil.runQuery(newAggOpRef, Arrays.asList(aggVar), newCtx, IRuleSetFactory.RuleSetKind.SAMPLING);

Large temp files such as these are created during this call

8124694528 Mar  8 12:06 JID$0.307$CDID$4$9$014392691293695800873.waf

and we run out of disk space.

This does not always happen

Do not know if this is data dependent.

couchbase-cli bucket-create -c http://localhost:9000 -u couchbase -p couchbase --bucket R --bucket-type couchbase --bucket-ramsize 800 --bucket-replica 0

/couchbase-cli bucket-create -c http://localhost:9000 -u couchbase -p couchbase --bucket S --bucket-type couchbase --bucket-ramsize 800 --bucket-replica 0

couchbase-cli bucket-create -c http://localhost:9000 -u couchbase -p couchbase --bucket T --bucket-type couchbase --bucket-ramsize 800 --bucket-replica 0

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cbimport csv -c http://localhost:9000 -u couchbase -p couchbase -b R -d file://./R.tbl -g key::%rand% --infer-types --field-separator '|'

cbimport csv -c http://localhost:9000 -u couchbase -p couchbase -b S -d file://./S.tbl -g key::%rand% --infer-types --field-separator '|'

/cbimport csv -c http://localhost:9000 -u couchbase -p couchbase -b T -d file://./T.tbl -g key::%rand% --infer-types --field-separator '|'

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R.tbl is included. The same file can be used for S.tbl and T.tbl