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https://issues.apache.org/jira/browse/PHOENIX-939?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13982125#comment-13982125
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James Taylor commented on PHOENIX-939:
--------------------------------------
In this example:
{code}
A = load 'hbase://query/SELECT ID,UPPER(NAME),NEXT VALUE FOR my_seq,MY_NUM+1
FROM HIRES WHERE AGE > 50' using
org.apache.phoenix.pig.PhoenixHBaseLoader('localhost') AS (a:chararray,
b:chararray, c: long, d:int);
{code}
it's a positional mapping, right? Is the AS (a:chararray, b:chararray, c: long,
d:int) optional? Does Pig restrict the names of the elements in a relation? If
the AS (a:chararray, b:chararray, c: long, d:int) is optional, then we can
fallback to the alias names used in the SELECT expressions, and if no alias,
then the name is the text of the expression. For example:
{code}
A = load 'hbase://query/SELECT ID,UPPER(NAME),NEXT VALUE FOR my_seq,MY_NUM+1
FROM HIRES WHERE AGE > 50' using
org.apache.phoenix.pig.PhoenixHBaseLoader('localhost');
{code}
The relation would be "ID", "UPPER(NAME)","NEXT VALUE FOR my_seq","MY_NUM+1".
Would this confuse Pig? Can you also refer to the elements of a relation by
position like you can in JDBC: resultSet.getInt(4)?
> Generalize SELECT expressions for Pig Loader
> --------------------------------------------
>
> Key: PHOENIX-939
> URL: https://issues.apache.org/jira/browse/PHOENIX-939
> Project: Phoenix
> Issue Type: Improvement
> Affects Versions: 5.0.0, 3.1, 4.1
> Reporter: James Taylor
> Assignee: maghamravikiran
> Fix For: 5.0.0, 3.1, 4.1
>
>
> The current Pig Loader requires that the query contain only column references
> in the SELECT expressions. Instead, we should allow any expression as that
> will provide more general utility. For example, built-in functions, sequence
> references, etc. could be used then.
> Validation can be done by simply compiling the query. This does all the
> validation required. It's ok if it's compiled twice if need be too.
> Pig doesn't know and likely wouldn't care if the expressions in the SELECT
> correspond to columns in Phoenix or general expressions. You can use the
> ColumnProjection.getName() method to get back an alias of the SELECT
> expression. If no alias is provided, then the String of the expression is
> returned. [~prkommireddi] - can you weigh in here? You can use the Phoenix
> RowProjector to iterate through each ColumnProjector you get back after the
> compile to get the alias of the select expression (i.e. you'd give this to
> Pig as the "column" name) plus the data type. Note that if this is
> problemattic, then you could likely generate an alias name if one is not
> present.
> For example:
> {code}
> RowProjector rowProj = queryPlan.getProjector();
> for (ColumnProjector colProj : rowProj.getColumnProjectors()) {
> String columnName = colProj.getName();
> PDataType dataType = colProj.getExpression().getDataType();
> }
> {code}
> If the SELECT expressions are simple column references, this would be exactly
> the same as is being done now. If the SELECT expressions are more complex
> expressions, this would work as well.
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