[teiid-issues] [JBoss JIRA] (TEIID-2794) ambiguous function calls are not properly handled

[Steven Hawkins (JIRA)]

     [ https://issues.jboss.org/browse/TEIID-2794?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Steven Hawkins resolved TEIID-2794.
-----------------------------------

    Resolution: Done


There are three classes of functions in Teiid:

System functions (effectively scoped to SYS) and are known at design time.
Pushdown functions (also effectively scoped to SYS) and are supplied by translators.
UDFs which are schema scoped (except for legacy function models) and are defined via metadata.

When we resolve, system functions take preference - no schema qualification is necessary.  But you can introduce for example a concat udf and call it as schema.concat(...).

Pushdown functions then take preference - but are currently a soft spot.  If it quite possible that two translators will declare the same function with the same root name, but we will currently not treat that as an ambiguity.  The primary reason is that in Designer pushdown functions must be redeclared in metadata to be used (either with the legacy function model or with source functions).  So we simply assume that first matching definition is correct.  However this is not ideal as we generally should consider all possible targets for the function to aid in pushdown.

Schema scoped functions are last in preference and require qualification if there are conflicting names.  Similar to the above there may be a need eventually to add a "conformed" feature for functions (beyond the existing udf / function support mechanism).
                
> ambiguous function calls are not properly handled
> -------------------------------------------------
>
>                 Key: TEIID-2794
>                 URL: https://issues.jboss.org/browse/TEIID-2794
>             Project: Teiid
>          Issue Type: Bug
>          Components: Query Engine
>    Affects Versions: 7.4
>            Reporter: Steven Hawkins
>            Assignee: Steven Hawkins
>             Fix For: 8.7
>
>
> For user defined or possibly translator functions that are given the same name the first exact match to the function name and types will be used as the function rather than reporting an ambiguous match.

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