On 29.08.24 18:33, Alexandra Wang wrote:
I’ve implemented the member and array accessors and attached two
alternative patches:
1. v1-0001-Add-JSON-JSONB-simplified-accessor.patch: This patch
enables dot access to JSON object fields and subscript access to
indexed JSON array elements by converting "." and "[]" indirection
into a JSON_QUERY JsonFuncExpr node.
2. v2-0001-Transform-JSON-dot-access-to-arrow-operator.txt: This
alternative patch implements dot access to JSON object fields by
transforming the "." indirection into a "->" operator.
The upside of the v1 patch is that it strictly aligns with the SQL
standard, which specifies that the simplified access is equivalent to:
JSON_QUERY (VEP, 'lax $.JC' WITH CONDITIONAL ARRAY WRAPPER NULL ON
EMPTY NULL ON ERROR)
However, the performance of JSON_QUERY might be suboptimal due to
function call overhead. Therefore, I implemented the v2 alternative
using the "->" operator.
Using the operator approach would also allow taking advantage of
optimizations such as
<https://www.postgresql.org/message-id/flat/CAKU4AWoqAVya6PBhn%2BBCbFaBMt3z-2%3Di5fKO3bW%3D6HPhbid2Dw%40mail.gmail.com>.
There is some uncertainty about the semantics of conditional array
wrappers. Currently, there is at least one subtle difference between
the "->" operator and JSON_QUERY, as shown:
That JSON_QUERY bug has been fixed.
I suggest you rebase both of your patches over this, just to double
check everything. But then I think you can drop the v1 patch and just
submit a new version of v2.
The patch should eventually contain some documentation. It might be
good starting to look for a good spot where to put that documentation.
It might be either near the json types documentation or near the general
qualified identifier syntax, not sure.
