[BUG] Explicit makeNullLiteral fails the schema merge for append and multisearch commands #4493
Description
What is the bug?
Both append and multisearch commands currently unions two search results by merging schema if the two search row types are different. The non existent fields in search A output, which comes from another search B, will be filled out with NULL literal by calling makeNullLiteral method to cast the NULL literal to the same type in merge schema.
Calcite RexBuilder makeNullLiteral internally calls makeCast method. PPL ExtendedRexBuilder can't handle cast UDT type to NULL literal.
How can one reproduce the bug?
// Append with birthdate UDT_TIMESTAMP:
source=account | fields account_name, age | head 2 |
append [ source=bank | fields account_name, age, birthdate | head 2 ]
// Multisearch with birthdate UDT_TIMESTAMP
| multisearch
[search source=account | fields age]
[search source=bank | fields age, birthdate]
What is the expected behavior?
Query should not fail.
What is your host/environment?
- OS: All
- Version [3.3]
- Plugins
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Do you have any additional context?
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