On Mon, Jul 29, 2013 at 2:16 AM, Andrew Tipton <and...@kiwidrew.com> wrote: > The attached patch adds four new SQL functions for the JSON type: > json_typeof(json) RETURNS text > json_is_object(json) RETURNS boolean > json_is_array(json) RETURNS boolean > json_is_scalar(json) RETURNS boolean > > The motivating use-case for this patch is the ability to easily create a > domain type for what RFC 4627 calls "json text", where the top-level value > must be either an object or array. An example of this usage is: > > CREATE DOMAIN json_document AS json CHECK (NOT json_is_scalar(VALUE)); > > An additional use-case arises when writing functions which can handle > arbitrary JSON values. This can be difficult when nested objects or arrays > are present or when the input may be either an array or an object. Many of > the built-in functions will raise an error when presented with an "invalid" > value, such as when giving an array to json_object_keys(). The > json_typeof() and json_is_*() functions should make it easier to call the > correct function in these cases, e.g.: > > CASE json_typeof($1) > WHEN 'object' THEN json_object_keys($1) > WHEN 'array' THEN json_array_elements($1) > ELSE $1 > END > > These new functions operate by making a single call to json_lex() to get the > first token of the JSON value; this token uniquely determines the value's > type. (Thanks to Merlin Moncure for suggesting this approach.) > > The patch also updates the "JSON Functions and Operators" section of the > docs to ensure that the words "value", "object", and "array" are used in a > consistent manner. "JSON object" and "JSON array" refer to parameters which > must be an object or an array or to results which are always an object or an > array. "JSON value" refers to parameters or results which may be any kind > of JSON.
you're welcome! :-). small point: Personally I would prune the supplied functions to json_typeof() and json_is_scalar(). These functions are in the public namespace so there is a certain minimum bang/buck ratio which IMNSHO json_is_object() and json_is_array() don't meet -- just call json_typeof() to get that info. merlin -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
