Apache Druid

This error occurs because Druid's SQL optimizer (based on Apache Calcite) requires the pattern argument of LIKE to be a string literal (constant) during query planning. When you apply functions like UPPER() directly to the pattern, the planner cannot reduce it to a literal at compile time, causing the error. A workaround is to pre-evaluate the function by using a Common Table Expression (CTE) or subquery, forcing the function result to be computed before the LIKE filter is applied. Example: WITH t AS (SELECT 'a string' AS col), t2 AS (SELECT col, UPPER(col) AS upper_col FROM t) SELECT * FROM t2 WHERE upper_col LIKE UPPER('a%'). Alternatively, ensure the pattern is a literal constant by moving the UPPER() call outside if possible. This is a known limitation in Druid versions up to at least 30.0.0, and may be addressed in future releases.

There is a known race condition in Druid (observed in v33.0.0) where redundant tasks with replicas > 1 conflict during segment publishing, causing this error. The only reliable workaround is to set the task replicas count to 1. This avoids the race but may cause ingestion downtime during worker shutdowns. The underlying bug is still unresolved; track issue #18330 for updates.