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• In Hive 2.2, upon successful completion of this operation the changes will be auto-committed.

Performance Note

SQL Standard requires that an error is raised if the ON clause is such that more than 1 row in source matches a row in target.  This check is computationally expensive and

may affect the overall runtime of a MERGE statement significantly.  hive.merge.cardinality.check=false may be used to disable the check at your own risk.  If the check is

disabled, but the statement has such cross join effect, it may lead to data corruption.

Notes

• 1,2 or 3 WHEN clauses may be present; at most 1 of each type: UPDATE/DELETE/INSERT
• WHEN NOT MATCHED must be the last WHEN clause
• If both UPDATE and DELETE clauses are present, the 1st one in the statement must include [AND <boolean expression>]
• Vectorization will be turned off for merge operations.  This is automatic and requires no action on the part of the user.  Non-delete operations are not affected.  Tables with deleted data can still be queried using vectorization.

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