运行sqoop命令时$ CONDITIONS的重要性

Question

每个sqoop导入查询中$ CONDITIONS的重要性是什么？

例如：

select col1, col2 from test_table where \$CONDITIONS

如果我需要在查询中放置自己的条件并且它有效，该怎么办？

Answer 1

Sqoop User Guide和Apache Sqoop cookbook解释了重要性。简而言之，Sqoop需要在查询中使用占位符来填充生成的切片以启用并行导入。

Answer 2

It will act as a place holder where sqoop replaces it to make the query works parallel. It is must to put $CONDTIONS when you are importing query results. Still you can place your condition as below,

Select col1,col2 from table where $CONDITIONS and "your condtion"

Note: you can directly see in stack trace what the condition sqoop places here at $CONDITIONS. Eg. The first thing you can see is the condition "where 1=0" to fetch the metadata or schema from source table.