On Mon, Jul 29, 2013 at 5:36 PM, Merlin Moncure <mmonc...@gmail.com> wrote: > 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.
+1, but I'm wondering why we need anything more than just json_typeof(). Doesn't that pretty much cover it? -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
