PySpark：如何在rdd join期间从左表中选择*

Question

如何在pyspark join中选择*

impression_rdd.join(
        click_rdd, 
        impression_rdd.session_id == click_rdd.session_id, 
        "left_outer"
    ).select(impression_rdd.*) <------- pseudo code; how do you do this?

基本上，sql等价

SELECT impression.* FROM impression LEFT JOIN click on (impression.session_id = click.session_id)

Answer 1

您可以简单地为您的伪代码添加别名和几个引号：

(impressions.alias("impressions")
    .join(clicks, ["id"], "left_outer")
    .select("impressions.*"))

Answer 2

zero323答案的另外两个等效结构：

(impressions.join(clicks, 'session_id', 'left_outer')
    .select(*impressions.columns))

如果您只有一列，请说＆＃39; count＆＃39;，要放入右侧表格，这可能更具可读性。

(impressions.join(clicks, 'session_id', 'left_outer')
    .drop('count'))