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This article will explain in detail the example analysis of predicate pushdown in Hive. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.

Predicate pushdown

The default generated execution plan executes the filter in a visible location, but in some cases, some filter expressions can be pushed closer to the operator that first saw this particular data.

For example, the following query:

Select

A. *

B. *

From

A join b on (a.col1 = b.col1)

Where a.col1 > 15 and b.col2 > 16

If there is no predicate push-down, the filter condition * * (a.col1 > 15 and b.col2 > 16) * * will be executed after the JOIN processing is completed. Therefore, in this case, JOIN will occur first, and more rows may be generated, and then the filtering operation will be performed.

Using predicate pushdown, these two predicates * * (a.col1 > 15 and b.col2 > 16) * * will be processed before JOIN, so it may filter out most of the data rows processed earlier in the connection from an and b, so it is recommended that you enable predicate pushdown.

You can enable predicate push-down by setting hive.optimize.ppd to true.

This is the end of SET hive.optimize.ppd=true 's article on "sample analysis of predicate pushdown in Hive". I hope the above content can be helpful to you, so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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