Charles Givre created DRILL-8169:
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             Summary: Add UDFs to HTTP Plugin to Facilitate Joins
                 Key: DRILL-8169
                 URL: https://issues.apache.org/jira/browse/DRILL-8169
             Project: Apache Drill
          Issue Type: Improvement
          Components: Storage - Other
    Affects Versions: 1.20.0
            Reporter: Charles Givre
            Assignee: Charles Givre
             Fix For: 2.0.0


There are some situations where a user might want to join data with an API 
result and the pushdowns prevent that from happening. The main situation where 
this happens is when 
an API has parameters which are part of the URL AND these parameters are 
dynamically populated via a join. 

In this case, there are two functions `http_get_url` and `http_get` which you 
can use to faciliate these joins. 

* `http_get('<storage_plugin_name>', <params>)`: This function accepts a 
storage plugin as input and an optional list of parameters to include in a URL.
* `http_get_url(<url>, <params>)`: This function works in the same way except 
that it does not pull any configuration information from existing storage 
plugins.

### Example Queries
Let's say that you have a storage plugin called `github` with an endpoint 
called `repos` which points to the url: https://github.com/orgs/\{org}/repos. 
It is easy enough to 
write a query like this:

```sql
SELECT * 
FROM github.repos
WHERE org='apache'
```
However, if you had a file with organizations and wanted to join this with the 
API, the query would fail. Using the functions listed above you could get this 
data as follows:

```sql
SELECT http_get('github.repos', `org`)
FROM dfs.`some_data.csvh`
```
or
```sql
SELECT http_get('https://github.com/orgs/\{org}/repos', `org`)
FROM dfs.`some_data.csvh`
```

** WARNING: This functionality will execute an HTTP Request FOR EVERY ROW IN 
YOUR DATA. Use with caution. **

 



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