Paul Rogers created DRILL-5069:
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Summary: MaterializeVisitor.visitSchemaPath silently ignores
missing fields
Key: DRILL-5069
URL: https://issues.apache.org/jira/browse/DRILL-5069
Project: Apache Drill
Issue Type: Bug
Affects Versions: 1.8.0
Reporter: Paul Rogers
Priority: Minor
Not sure if this is a bug or a feature...
The test {{ExpressionTest}} tests various expressions by parsing them and
generating code. The expression under test in the
{{testExprParseLowerExponent}} test is:
{code}
multiply(`$f0`, 1.0e-4)
{code}
The first argument appears to be a reference to the first field (0-based
indexes) in the given {{RecordBatch}}:
{code}
getExpressionCode("multiply(`$f0`, 1.0e-4)", batch);
{code}
Because of the way the mocked {{RecordBatch}} is handled, resolving {{$f0}}
will produce a null result from: {{batch.getValueVectorId("$f0");}}. The code
in {{MaterializeVisitor.visitSchemaPath}} logs a warning when the field
reference is not found:
{code}
Unable to find value vector of path $f0, returning null instance.
{code}
The code for building up the multiply function appears to treat this case as a
the equivalent of:
{code}
multiply(1.0e-4)
{code}
That is, it just ignores the missing field.
This seems to invite errors. Would expect that if code elsewhere in Drill
generated the a reference to a missing field, that Drill should flag this as a
serious error. Said another way, if the rest of Drill works properly, the
missing field reference scenario should never occur in production.
For the particular test in question, use the mocking mechanism to pretend that
the target field exists. See the {{testSchemaExpression}} test for an example.
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