CAST behavior inconsistent between Mimir and Spark

[okennedy]

The following query behaves differently depending on whether CAST is evaluated in Mimir or in Spark.

SELECT CAST('.' AS int)

In Mimir it returns NULL, while in Spark it returns 0.

• [ ] Short-term fix: Make Mimir cast '.' to 0.
• [ ] Long-term fix: Switch over to Spark's cast operation directly.