hive uses php script to complete map/reduce

hive sql has a relatively powerful function, which is that it can use external scripts to complete map/reduce. Usage is as follows:
TRANSFORM(….) USING ‘….’ AS (….).
USING can be processed using php scripts. See the example below for specific usage.

①, create a table:

<code>hive> CREATE TABLE <span>`member`</span>(
    >   <span>`id`</span><span>int</span>,
    >   <span>`user_name`</span><span>string</span>,
    >   <span>`passwd`</span><span>string</span>
    > )
    > row <span>format</span> delimited
    > fields terminated by <span>"\t"</span><span>//这句很必要，不然下面的文件导入会导致所有的值都变成null </span>
    > stored as textfile;</code>

②, prepare the following data /tmp/member.dat

<code>1     zhangsan     zs1024
2     lisi     ls1991
3     wangwu     ww2001
4     liumang     lm1234
5     linxing     lx1990</code>

③, import the data

<code>hive> <span>load</span> data <span>local</span> inpath <span>'/tmp/member.dat'</span> into <span>table</span> member;</code>

You can see:

<code>hive> <span>select</span> * <span>from</span> member;
OK
<span>1</span>       zhangsan        zs1024
<span>2</span>       lisi    ls1991
<span>3</span>       wangwu  ww2001
<span>4</span>       liumang lm1234
<span>5</span>       linxing lx1990</code>

The data is ready, now we are relatively third The column is encrypted once with md5. We use a php script to handle it. The code of the php script (/tmp/changePasswd.php) is as follows:

<code><span><span><?php</span><span>while</span>(!feof(STDIN)){
     <span>$line</span> = rtrim(fgets(STDIN), <span>"\n"</span>);      <span>//逐行读取</span><span>if</span> (<span>empty</span>(<span>$line</span>)) <span>continue</span>;     <span>//空，跳出当次循环</span><span>$data</span> = explode(<span>"\t"</span>, <span>$line</span>);    <span>//将切分出来的数组保存起来，下面判断使用</span><span>foreach</span>(<span>$data</span><span>as</span> &<span>$val</span>){
          <span>$val</span> = md5(<span>$val</span>);
     }
     <span>unset</span>(<span>$val</span>);
     <span>echo</span> implode(<span>"\t"</span>, <span>$data</span>) . <span>"\n"</span>;
}</span></code>

④. Add the php script to hive.

<code>hive> <span>add</span> file /tmp/changePasswd<span>.php</span><span>;</span></span></span></code>

⑤, use php script to execute map/reduce

<code>hive> insert overwrite table member
    > select TRANSFORM(<span>`i</span>d<span>`,</span><span>`u</span>ser_name<span>`,</span><span>`p</span>asswd<span>`)</span> using <span>"/usr/bin/php changePasswd.php"</span>
    > as (<span>`i</span>d<span>`,</span><span>`u</span>ser_name<span>`,</span><span>`p</span>asswd<span>`)</span> from member<span>;</span></code>

Finally, we can see that the data in the passwd column has changed:

<code>hive> <span>select</span> * <span>from</span> member;
OK
<span>1</span>       zhangsan        d03eed89429cc3006cc279322c2800c5
<span>2</span>       lisi    <span>063401506</span>c9d9f0e49a706e3779b7428
<span>3</span>       wangwu  ac5a8109dbbb46c9f69ffd5fc93c11f8
<span>4</span>       liumang fda8b97fd723bdbf6a754812b5ecec27
<span>5</span>       linxing <span>4035378</span>ace8936e93d95aa77e7e224d4</code>

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The above introduces hive's use of PHP scripts to complete map/reduce, including aspects of it. I hope it will be helpful to friends who are interested in PHP tutorials.