Subject: Re: remaining sql/json patches

From: jian he <[email-masked]>
Date: Fri, 15 Mar 2024 18:30:18 +0800

On Mon, Mar 11, 2024 at 11:30 AM jian he <[email-masked]> wrote:
>
> On Sun, Mar 10, 2024 at 10:57 PM jian he <[email-masked]> wrote:
> >
> > one more issue.
>
> Hi
> one more documentation issue.
> after applied V42, 0001 to 0003,
> there are 11 appearance of `FORMAT JSON` in functions-json.html
> still not a single place explained what it is for.
>
> json_query ( context_item, path_expression [ PASSING { value AS
> varname } [, ...]] [ RETURNING data_type [ FORMAT JSON [ ENCODING UTF8
> ] ] ] [ { WITHOUT | WITH { CONDITIONAL | [UNCONDITIONAL] } } [ ARRAY ]
> WRAPPER ] [ { KEEP | OMIT } QUOTES [ ON SCALAR STRING ] ] [ { ERROR |
> NULL | EMPTY { [ ARRAY ] | OBJECT } | DEFAULT expression } ON EMPTY ]
> [ { ERROR | NULL | EMPTY { [ ARRAY ] | OBJECT } | DEFAULT expression }
> ON ERROR ])
>
> FORMAT JSON seems just a syntax sugar or for compatibility in json_query.
> but it returns an error when the returning type category is not
> TYPCATEGORY_STRING.
>
> for example, even the following will return an error.
> `
> CREATE TYPE regtest_comptype AS (b text);
> SELECT JSON_QUERY(jsonb '{"a":{"b":"c"}}', '$.a' RETURNING
> regtest_comptype format json);
> `
>
> seems only types in[0] will not generate an error, when specifying
> FORMAT JSON in JSON_QUERY.
>
> so it actually does something, not a syntax sugar?
>

SELECT * FROM JSON_TABLE(jsonb'[{"aaa": 123}]', 'lax $[*]' COLUMNS
(js2 text format json PATH '$' omit quotes));
SELECT * FROM JSON_TABLE(jsonb'[{"aaa": 123}]', 'lax $[*]' COLUMNS
(js2 text format json PATH '$' keep quotes));
SELECT * FROM JSON_TABLE(jsonb'[{"aaa": 123}]', 'lax $[*]' COLUMNS
(js2 text PATH '$' keep quotes)); -- JSON_QUERY_OP
SELECT * FROM JSON_TABLE(jsonb'[{"aaa": 123}]', 'lax $[*]' COLUMNS
(js2 text PATH '$' omit quotes)); -- JSON_QUERY_OP
SELECT * FROM JSON_TABLE(jsonb'[{"aaa": 123}]', 'lax $[*]' COLUMNS
(js2 text PATH '$')); -- JSON_VALUE_OP
SELECT * FROM JSON_TABLE(jsonb'[{"aaa": 123}]', 'lax $[*]' COLUMNS
(js2 json PATH '$')); -- JSON_QUERY_OP
comparing these queries, I think 'FORMAT JSON' main usage is in json_table.

CREATE TYPE regtest_comptype AS (b text);
SELECT JSON_QUERY(jsonb '{"a":{"b":"c"}}', '$.a' RETURNING
regtest_comptype format json);
ERROR:  cannot use JSON format with non-string output types
LINE 1: ..."a":{"b":"c"}}', '$.a' RETURNING regtest_comptype format jso...
                                                             ^
the error message is not good, but that's a minor issue. we can pursue it later.
-----------------------------------------------------------------------------------------
SELECT JSON_QUERY(jsonb 'true', '$' RETURNING int KEEP QUOTES );
SELECT JSON_QUERY(jsonb 'true', '$' RETURNING int omit QUOTES );
SELECT JSON_VALUE(jsonb 'true', '$' RETURNING int);
the third query returns integer 1, not sure this is the desired behavior.
it obviously has an implication for json_table.
-----------------------------------------------------------------------------------------
in jsonb_get_element, we have something like:
if (jbvp->type == jbvBinary)
{
container = jbvp->val.binary.data;
have_object = JsonContainerIsObject(container);
have_array = JsonContainerIsArray(container);
Assert(!JsonContainerIsScalar(container));
}

+ res = JsonValueListHead(&found);
+ if (res->type == jbvBinary && JsonContainerIsScalar(res->val.binary.data))
+ JsonbExtractScalar(res->val.binary.data, res);
So in JsonPathValue, the above (res->type == jbvBinary) is unreachable?
also see the comment in jbvBinary.

maybe we can just simply do:
if (res->type == jbvBinary)
Assert(!JsonContainerIsScalar(res->val.binary.data));
-----------------------------------------------------------------------------------------
+<synopsis>
+JSON_TABLE (
+  <replaceable>context_item</replaceable>,
<replaceable>path_expression</replaceable> <optional> AS
<replaceable>json_path_name</replaceable> </optional> <optional>
PASSING { <replaceable>value</replaceable> AS
<replaceable>varname</replaceable> } <optional>, ...</optional>
</optional>
+  COLUMNS ( <replaceable
class="parameter">json_table_column</replaceable> <optional>,
...</optional> )
+  <optional> { <literal>ERROR</literal> | <literal>EMPTY</literal> }
<literal>ON ERROR</literal> </optional>
+  <optional>
+    PLAN ( <replaceable class="parameter">json_table_plan</replaceable> ) |
+    PLAN DEFAULT ( { INNER | OUTER } <optional> , { CROSS | UNION } </optional>
+                 | { CROSS | UNION } <optional> , { INNER | OUTER }
</optional> )
+  </optional>
+)

based on the synopsis
the following query should not be allowed?
SELECT *FROM (VALUES ('"11"'), ('"err"')) vals(js)
LEFT OUTER JOIN  JSON_TABLE(vals.js::jsonb, '$' COLUMNS (a int PATH
'$') default '11' ON ERROR) jt ON true;

aslo the synopsis need to reflect case like:
SELECT *FROM (VALUES ('"11"'), ('"err"')) vals(js)
LEFT OUTER JOIN  JSON_TABLE(vals.js::jsonb, '$' COLUMNS (a int PATH
'$') NULL ON ERROR) jt ON true;