HBase REST Filter ( SingleColumnValueFilter )

Question

I cannot figure out how to use filters in the HBase REST interface (HBase 0.90.4-cdh3u3). The documentation just gives me a schema definition for a "string", but doesn't show how to use it.

So, I'm able to do this:

curl -v -H 'Content-Type: text/xml' -d '<Scanner startRow="ddo" stopRow="ddp" batch="1024"/>' 'http://hbasegw:8080/table/scanner' 

and then retrieve with

curl -s -H "Content-Type: text/xml" http://hbasegw:8080/table/scanner/13293426893883128482b | tidy -i -q -xml 

But now I want to use a SingleColumnValueFilter and have to encode that somehow in the XML. Does anyone have an example for this?

Thanks, Mario

Answer 1

Filter fields in the Scanner XML are strings formatted as JSON. Since the JSON for the filter has many quotes in it, I recommend using a separate file for curl's -d parameter, to avoid the single quote.

curl -v -H "Content-Type:text/xml" -d @args.txt http://hbasegw:8080/table/scanner

Where the file args.txt is:

<Scanner startRow="cm93MDE=" endRow="cm93MDg=" batch="1024">     <filter>     {         "latestVersion":true, "ifMissing":true,          "qualifier":"Y29sMQ==", "family":"ZmFtaWx5",          "op":"EQUAL", "type":"SingleColumnValueFilter",          "comparator":{"value":"MQ==","type":"BinaryComparator"}     }     </filter> </Scanner> 

How do you discover how the JSON filter string should look like? Here's an easy way through Java code that spits out the stringified filter given a standard Filter object from HBase's Java API.

SingleColumnValueFilter filter = new SingleColumnValueFilter(     Bytes.toBytes("family"),     Bytes.toBytes("col1"),     CompareFilter.CompareOp.EQUAL,     Bytes.toBytes("1") ); System.out.println(ScannerModel.stringifyFilter(filter)); 

Notice that the JSON and the XML require data encoded in Base64. I've tested the above curl command on a table and it worked just fine.

In case you are wondering, yes, the REST API for scanners is not yet as developer-friendly as it can get.