[
https://issues.apache.org/jira/browse/PHOENIX-538?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14497724#comment-14497724
]
James Taylor commented on PHOENIX-538:
--------------------------------------
Thanks for the revisions, [~rajeshbabu].
bq. You mean after parsing the statement we need to check for all UDFParse
nodes in the statement and have list.
In PhoenixSQL.g, you can just add a new member variable for a List<
UDFParseNode>. You'd add to this list where factory.function() throws because
it can't find the function in a catch block. You'd clear the list in the
finally block of the oneStatement rule, as this would be the scope of where
you'd want to collect this list. And you'd pass in this list to the appropriate
factory method (like factory.select(), factory.delete(), factory.upsert(),
etc.). Another place you could potentially do this is in the
StatementNormalizer visitor (which I believe is uniformly called). You could
have a visitor for FunctionParseNode that checks if it's a UDFParseNode and
collect them. Make sure you transfer over the List on the statements when the
statement is cloned.
{code}
// --------------------------------------
// The Parser
@parser::members
{
/**
* used to turn '?' binds into : binds.
*/
private int anonBindNum;
private ParseNodeFactory factory;
private ParseContext.Stack contextStack = new ParseContext.Stack();
{code}
How are you going to handle when the UDF is invoked on the client side, as you
won't be able to rely on the dynamic class loading that HBase is able to do? A
function will be evaluated on the client side if it's used in the SELECT
clause, for example.
Any tests yet?
> Support UDFs
> ------------
>
> Key: PHOENIX-538
> URL: https://issues.apache.org/jira/browse/PHOENIX-538
> Project: Phoenix
> Issue Type: Task
> Reporter: James Taylor
> Assignee: Rajeshbabu Chintaguntla
> Fix For: 5.0.0, 4.4.0
>
> Attachments: PHOENIX-538-wip.patch, PHOENIX-538_v1.patch
>
>
> Phoenix allows built-in functions to be added (as described
> [here](http://phoenix-hbase.blogspot.com/2013/04/how-to-add-your-own-built-in-function.html))
> with the restriction that they must be in the phoenix jar. We should improve
> on this and allow folks to declare new functions through a CREATE FUNCTION
> command like this:
> CREATE FUNCTION mdHash(anytype)
> RETURNS binary(16)
> LOCATION 'hdfs://path-to-my-jar' 'com.me.MDHashFunction'
> Since HBase supports loading jars dynamically, this would not be too
> difficult. The function implementation class would be required to extend our
> ScalarFunction base class. Here's how I could see it being implemented:
> * modify the phoenix grammar to support the new CREATE FUNCTION syntax
> * create a new UTFParseNode class to capture the parse state
> * add a new method to the MetaDataProtocol interface
> * add a new method in ConnectionQueryServices to invoke the MetaDataProtocol
> method
> * add a new method in MetaDataClient to invoke the ConnectionQueryServices
> method
> * persist functions in a new "SYSTEM.FUNCTION" table
> * add a new client-side representation to cache functions called PFunction
> * modify ColumnResolver to dynamically resolve a function in the same way we
> dynamically resolve and load a table
> * create and register a new ExpressionType called UDFExpression
> * at parse time, check for the function name in the built in list first (as
> is currently done), and if not found in the PFunction cache. If not found
> there, then use the new UDFExpression as a placeholder and have the
> ColumnResolver attempt to resolve it at compile time and throw an error if
> unsuccessful.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
