Ad hoc tables are in-memory tables generated by the defineTable() function. Adjusting this limit allows you to balance between providing flexibility for complex queries with multiple ad hoc tables while preventing excessive resource usage from too many in-memory tables.

Tables are automatically cleaned up when the creating query completes or the session expires.

This setting works in conjunction with:

When running complex queries with correlations or multiple aggregations, consider the cumulative memory impact of all of the above limits together.

Increase the limit if users frequently encounter "limit exceeded" errors. Decrease if experiencing memory pressure or OutOfMemoryError exceptions during complex queries with multiple ad hoc tables.

When the limit is reached, attempts to create additional ad hoc tables via defineTable() will fail with an error message: "Ad hoc table limit exceeded (X/Y tables in use)". The query will terminate with an error status. Existing ad hoc tables remain unaffected and continue to function normally until they are automatically cleaned up or the query session ends.

Warning logs, such as "Ad hoc table usage high: 8/10 tables in use", are generated at 80% capacity. When troubleshooting limit-related query failures, search the system repositories for "ad hoc table limit" messages.