Constant mz_sql::plan::typeconv::STRING_REG_CAST_TEMPLATE

const STRING_REG_CAST_TEMPLATE: &str = "
(SELECT
CASE
    WHEN $1 IS NULL THEN NULL
-- Handle OID-like input, if available via {2}
    WHEN {2} AND pg_catalog.substring($1, 1, 1) BETWEEN '0' AND '9' THEN
        $1::pg_catalog.oid::pg_catalog.{0}
    ELSE (
    -- String case; look up that the item exists
        SELECT o.oid
        FROM mz_unsafe.mz_error_if_null(
            (
                -- We need to ensure a distinct here in the case of e.g. functions,
                -- where multiple items share a GlobalId.
                SELECT DISTINCT id AS name_id
                FROM mz_internal.mz_resolve_object_name('{0}', $1)
            ),
            -- TODO: Support the correct error code for does not exist (42883).
            '{1} \"' || $1 || '\" does not exist'
        ) AS i (name_id),
        -- Lateral lets us error separately from DNE case
        LATERAL (
            SELECT
                CASE
            -- Handle too many OIDs
                WHEN mz_catalog.list_length(mz_catalog.list_agg(oid)) > 1 THEN
                    mz_unsafe.mz_error_if_null(
                        NULL::pg_catalog.{0},
                        'more than one {1} named \"' || $1 || '\"'
                    )
            -- Resolve object name's OID if we know there is only one
                ELSE
                    CAST(mz_catalog.list_agg(oid)[1] AS pg_catalog.{0})
                END
            FROM mz_catalog.mz_objects
            WHERE id = name_id
            GROUP BY id
        ) AS o (oid)
    )
END)";

STRING to REG*

A reg* type represents a specific type of object by oid.

Casting from a string to a reg*:

• Accepts a string that looks like an OID and converts the value to the specified reg* type. This is available in all cases except explicitly casting text values to regclass (e.g. SELECT '2'::text::regclass)
• Resolves non-OID-appearing strings to objects. If this string resolves to more than one OID (e.g. functions), it errors.

The below code provides a template to accomplish this for various reg* types. Arguments in order are:

• 0: type catalog name this is casting to
• 1: the category of this reg for the error message
• 2: Whether or not to permit passing through numeric values as OIDs