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Sorabh Hamirwasia updated DRILL-6824: ------------------------------------- Component/s: (was: Execution - Data Types) > Drill Query on MapRDB JSON table failing on schema SchemaChangeException, the > only distinct Values are NULL and Text > -------------------------------------------------------------------------------------------------------------------- > > Key: DRILL-6824 > URL: https://issues.apache.org/jira/browse/DRILL-6824 > Project: Apache Drill > Issue Type: Bug > Affects Versions: 1.14.0 > Reporter: Gautam Parai > Assignee: Gautam Parai > Priority: Major > Labels: ready-to-commit > Fix For: 1.15.0 > > Original Estimate: 24h > Remaining Estimate: 24h > > Drill Query on MapR DB JSON Table or it View fails with a > SchemaChangeException. The only distinct values is NULL and some Text. > The issue is that when Drill sees a NULL or does not see any values for a > column in the first batch it assumes the type as NULLABLE INT. Subsequently, > when the data shows up and it is different from NULLABLE INT there is a > schema change. Operators e.g. aggregators etc. cannot handle such a Schema > Change and throw a SchemaChangeException. > > One of the short-term solution implemented in this fix: Add a CAST expression > which will cast null values to the target type. Hence, we would never see a > SchemaChange due to NULLs. However, the MapRDB Reader code was written > differently than other reader and was hitting a SchemaChangeException. The > code was changed to make it similar to other scans i.e. emit a new batch > whenever a schema change is encountered. -- This message was sent by Atlassian JIRA (v7.6.3#76005)