HiveSql&SparkSql -- use left semi join to optimize subqueries of in and exists types
Introduction to LEFT SEMI JOIN
The main use scenario of SEMI JOIN (equivalent to LEFT SEMI JOIN) is to solve EXISTS IN. LEFT SEMI JOIN is a more efficient implementation of IN/EXISTS sub query. Although LEFT SEMI JOIN contains LEFT, its implementation effect is equivalent to INNER JOIN, but the JOIN result only takes the columns in the orig ...
Posted by Waldir on Mon, 31 Jan 2022 15:40:32 +0100
Summary of association processing methods in ES
preface
This section mainly introduces the processing method of association relationship in ES.
1, Scheme summary
According to the introduction in the authoritative guide to Elasticsearch and the official website, ES mainly deals with association relationships in the following ways:
Application layer AssociationUnplanned datanested object ...
Posted by Coco on Mon, 03 Jan 2022 16:54:15 +0100