Hive 0.7以上新版本增加的更有效率的两个函数

hive 0.7版本以后新增了两个函数，比原来的函数更能提高运行效率。

json_tuple

使用方法与介绍

json_tuple(jsonStr, p1, p2, ..., pn) - like get_json_object, but it takes multiple names and return a tuple. All the input parameters and output column types are string.

A new json_tuple() UDTF is introduced in hive 0.7. It takes a set of names (keys) and a JSON string, and returns a tuple of values using one function. This is much more efficient than calling GET_JSON_OBJECT to retrieve more than one key from a single JSON string. In any case where a single JSON string would be parsed more than once, your query will be more efficient if you parse it once, which is what JSON_TUPLE is for. As JSON_TUPLE is a UDTF, you will need to use the LATERAL VIEW syntax in order to achieve the same goal

使用实例

get_json_object函数

select a.timestamp, get_json_object(a.appevents, '$.eventid'), get_json_object(a.appenvets, '$.eventname') from log a; 使用json_tuple函数方法

select a.timestamp, b.*

from log a lateral view json_tuple(a.appevent, 'eventid', 'eventname') b as f1, f2;

parse_url_tuple

使用方法与介绍

parse_url_tuple(url, partname1, partname2, ..., partnameN) - extracts N (N>=1) parts from a URL.

It takes a URL and one or multiple partnames, and returns a tuple. All the input parameters and output column types are string.

The parse_url_tuple() UDTF is similar to parse_url(), but can extract multiple parts of a given URL, returning the data in a tuple. Values for a particular key in QUERY can be extracted by appending a colon and the key to the partToExtract argument, e.g. parse_url_tuple('http://facebook.com/path1/p.php?k1=v1&k2=v2#Ref1', 'QUERY:k1', 'QUERY:k2') returns a tuple with values of 'v1','v2'. This is more efficient than calling parse_url() multiple times. All the input parameters and output column types are string.

使用实例

SELECT b.*

FROM src LATERAL VIEW parse_url_tuple(fullurl, 'HOST', 'PATH', 'QUERY', 'QUERY:id') b as host, path, query, query_id LIMIT 1;