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https://issues.apache.org/jira/browse/METAMODEL-224?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15096832#comment-15096832
]
ASF GitHub Bot commented on METAMODEL-224:
------------------------------------------
Github user kaspersorensen commented on a diff in the pull request:
https://github.com/apache/metamodel/pull/85#discussion_r49636369
--- Diff:
core/src/test/java/org/apache/metamodel/QueryPostprocessDataContextTest.java ---
@@ -294,6 +294,29 @@ public void testScalarFunctionWhere() throws Exception
{
ds.close();
}
+ public void testScalarFunctionConcat() throws Exception {
+ MockDataContext dc = new MockDataContext("sch", "tab", "1");
+ Table table = dc.getDefaultSchema().getTables()[0];
+ MutableColumn col = new MutableColumn("foo").setTable(table);
+ MutableColumn col2 = new MutableColumn("bar").setTable(table);
+ Object[] functionParams = new Object[3];
+ functionParams[0] = col;
+ functionParams[1] = "$";
+ functionParams[2] = col2;
+ Query query = dc.query()
+ .from(table)
+ .select(col, FunctionType.CONCAT, functionParams)
--- End diff --
But my concern is actually that in this case you may also have many columns
(or rather I prefer to think of it as SelectItems because even those could (one
day when we support it) be function calls), for instance:
```
SELECT CONCAT( name, " ", TO_STRING(age), " - ", hometown ) FROM people
```
... but today we might settle on "only" supporting simple selectitems as
parameters, so:
```
SELECT CONCAT( name, " ", age, " - ", hometown ) FROM people
```
... that would for me be a reasonable limitation for a first version.
But my worry is that if it's a problem to not have a column in the
SelectItem then I'm sure it's also a problem that we have (in the above case)
essentially 3 columns referred. I can imagine that this would work mostly then
based on coincidence (maybe age and hometown are also materialized by some
coincidence rather than conscious design). I know this is maybe making life
hard on you, but it feels wrong to go ahead with a solution that feels unstable
because of this.
> Support CONCAT function
> -----------------------
>
> Key: METAMODEL-224
> URL: https://issues.apache.org/jira/browse/METAMODEL-224
> Project: Apache MetaModel
> Issue Type: New Feature
> Reporter: Alberto
> Priority: Minor
>
> As we now support scalar functions it would be great to add support for a
> CONCAT function that allow us to concatenate and append strings to the query
> results.
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