[CALCITE-582] EnumerableTableScan broken when table has single column

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.0.0-incubating
• Assignee: Julian Hyde
• Reporter: Julian Hyde
• Created: 31/Jan/15 18:47
• Updated: 08/Feb/15 08:56
• Resolved: 06/Feb/15 19:32

Description

Vladimir writes:

The release brings regression in terms of
AbstractQueryableTable(Object[]) vs EnumerableTableScan interaction.

I am not sure what is the best way to solve it.

I suspect EnumerableTableScan users are impacted.

Historically, Calcite treated AbstractQueryableTable(Object[].class)
in a tricky way:
1) If the row type has more than one column, then Calcite expects
Enumerator<Object[]>
2) If the row type has just a single column, then Calcite expects
"unboxed Object[]".

In CALCITE-488 this behavior was broken so for Object[].class tables
Calcite always expects Object[] boxed rows.
From one view this new behavior is "less surprising", however the
change was not intended.

For instance, smart-csv-example is broken since it tries to use
adaptive enumerator type depending on the number of projected columns.
In particular, the change impacts my mat-calcite-plugin and I have no
idea how I missed that when I was testing previous RC.

I would suggest revert to the old mode when Object[].class kind of
tables skip Object[] array for single-column rows.

Well, the PhysType vs elementType API should be improved, however I
would not want that improvement to hold the train.

And further:

Here's additional test case:
https://github.com/vlsi/incubator-calcite/commit/f8ec9591ee6be3ce670dfeeb7ff076ae0c9f1345

testModelCustomTableArrayRowSingleColumn breaks with
java.lang.ClassCastException: java.lang.Integer cannot be cast to
[Ljava.lang.Object;
at Baz$1.apply(ANONYMOUS.java:11)

A naive fix (https://github.com/vlsi/incubator-calcite/commit/20d274c0526499cf06e0e61c6d49faf5a8ae7296)
breaks ScannableTable: it looks like scan always returns Object[],
however EnumerableTableScan requires scalars for single columns.