| 摘要 |
In a database management system, when the table to be accessed by a statement is partitioned, a respective partition scan operator is used to access rows of each respective database table partition. A fan out operator receives requests from a calling application to access rows from table, and responds by sending requests for rows to the partition scan operators. It receives rows of the table from the partition scan operators and sends the received rows of the database table to another node in the execution tree. Each of the partition scan operators responds to the requests for rows by returning to the fan out operator qualifying rows, if any, from the corresponding table partition. If the statement being executed includes an embedded delete or update operation, the qualifying rows are deleted or updated at the same time that the qualifying rows are returned to the fan out operator. Control is returned to the calling application only after all rows deleted or updated by the partition scan operators have been sent to the calling application. When the statement being executed is a streaming mode query, the fan out operator sends non-blocking requests to the partition scan operators so that when one access to one partition is blocked, rows from another partition are processed.
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