Hi Peter, Thank you so much for helping!
On Mon, Sep 16, 2024 at 12:44 PM Peter Eisentraut <pe...@eisentraut.org> wrote: > > 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>. OK, that makes sense. > > 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. Done. I rebased both patches and confirmed they have the same test outputs. I attached v3, which also adds JSON subscript support on top 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. Right, I’m not sure either. A third option, I think, would be to include it in the JSON Functions and Operators section [1]. [1] https://www.postgresql.org/docs/devel/functions-json.html Best, Alex
v3-0001-Add-JSON-JSONB-simplified-accessor.patch
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