Status

Current state: [One of "Under Discussion", "Accepted", "Rejected"]

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Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

Motivation

Stored procedure provides a convenient way to encapsulate complex logic to perform data manipulation or administrative tasks in external storage systems.  It's widely used in traditional databases and popular compute engines like Trino for it's convenience. 

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Note: In this FLIP, we don't intend to allow users to customize their own stored procedure  for we don't want to expose too much to users too early.

Public Interfaces

Syntax

We propose the following synatax to call a stored procedure:

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Note: The expression  can be a function call, but should be reduced  to literal value. Otherwise, it'll throw an exception.

Public interfaces changes

First, we propose a new interface Procedure for stored procedure. The stored procedure providers are expected to implement Procedure  to define their own procedure.

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/** Exception for trying to operate on a procedure that doesn't exist. */
@PublicEvolving
public class ProcedureNotExistException extends Exception {
    private static final String MSG = "Procedure %s does not exist in Catalog %s.";

    public ProcedureNotExistException(String catalogName, ObjectPath functionPath) {
        this(catalogName, functionPath, null);
    }

    public ProcedureNotExistException(
            String catalogName, ObjectPath functionPath, Throwable cause) {
        super(String.format(MSG, functionPath.getFullName(), catalogName), cause);
    }
}

Proposed Changes

1:  In method FunctionCatalogOperatorTable#lookupOperatorOverloads, if the passed SqlFunctionCategory  is USER_DEFINED_PROCEDURE , get the procedure in Catalog  with the given SqlIdentifier,  and then wrap it to BridginSqlProcedure  which is intance of SqlFunction.

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5: Get the result of procedure#call(xxx) , which should be CloseableIterator. Build a TableResult  with the so that the SqlClient can show the result of the call procedure to users.

Compatibility, Deprecation, and Migration Plan

• What impact (if any) will there be on existing users? 
• If we are changing behavior how will we phase out the older behavior? 
• If we need special migration tools, describe them here.
• When will we remove the existing behavior?

Test Plan

Describe in few sentences how the FLIP will be tested. We are mostly interested in system tests (since unit-tests are specific to implementation details). How will we know that the implementation works as expected? How will we know nothing broke?

Rejected Alternatives

If there are alternative ways of accomplishing the same thing, what were they? The purpose of this section is to motivate why the design is the way it is and not some other way.