使用withBatch处理BatchUpdateException

问题描述

我正在遍历一组对象，将它们插入到PostgreSQL数据库中，如下所示：

I am looping over a set of objects inserting them into my PostgreSQL database like this:

sql.withTransaction {
    try {
        sql.withBatch(1000, 'insert into category (id, version, name, parent_id) values (:id, :version, :name, :parent_id);') { stmt ->
            categoryInserts.each {
                try {
                    stmt.addBatch([id: it.id, version: 0, name: it.name, parent_id: it.parent?.id])
                } catch (SQLException e) {
                    log.error("Category ${it.name} with parent ${it.parent?.id} could not be inserted.")
                }
            }
         }
      } catch (BatchUpdateException e) {
          log.error("Categories could not be inserted.")
      }
      sql.commit()
}

类别表上有一个唯一的约束（名称，parent_id）。如果违反了约束，则程序将捕获BatchUpdateException，并且不会插入后续对象。不幸的是，在执行addBatch方法时并没有引发异常。

There is a unique constraint (name, parent_id) on the category table. If the constraint is violated the program catches a BatchUpdateException and subsequent objects are not inserted. Unfortunately the exception is not thrown while executing the addBatch-method.

有什么方法可以继续withBatch语句，以便忽略重复项并插入新记录吗？批处理插入不提供这种行为对我来说似乎很奇怪。

Is there any way to continue with the withBatch statement, so that duplicates are ignored and new records are inserted? It seems strange to me that a batch-Insert does not offer this behaviour.

推荐答案

我能够通过帖子解决此问题在Alexandros评论中提到。现在的解决方案如下所示：

I was able to solve this with the post mentioned in Alexandros comment. The solution now looks like this:

sql.withTransaction {
    try {
        sql.withBatch(1000, 'insert into category (id, version, name, parent_id) ' +
        'select :id, :version, :name, :parent_id ' +
        'where not exists (select name, parent_id from category where name = :name and parent_id = :parent_id);') { stmt ->
            categoryInserts.each {
                try {
                    stmt.addBatch([id: it.id, version: 0, name: it.name, parent_id: it.parent?.id])
                } catch (SQLException e) {
                  log.error("Category ${it.name} with parent ${it.parent?.id} could not be inserted.")
                }
            }
        }
    } catch (BatchUpdateException e) {
        log.error("Categories could not be inserted.", e)
    }

    sql.commit()
}

请注意，这是通过postgresql解决的SQL的方言。对于其他DBMS，在withBatch方法中使用SQL过程可能是一种有用的方法。

Be aware that this is solved with the postgresql dialect of SQL. For other DBMSs it might be a useful approach to use a SQL-procedure in the withBatch-method.

如果有人知道使用标准SQL进行此操作的方法，请给我一个提示。

If someone knows a way to do this with a standard-SQL, please give me a hint.

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