On Sat, May 10, 2014 at 5:54 PM, Tom Lane <t...@sss.pgh.pa.us> wrote:
> I'm not sure whether we have consensus to rename jsonb_hash_ops to
> jsonb_path_ops, but since time is so short I went ahead and made a draft
> patch to do so (attached). Probably the most interesting part of this is
> the new text in json.sgml explaining the difference between the two
> opclasses. I also added a paragraph about the empty-query hazard that
> Peter mentions. Do people think this discussion is correct and useful?
I for one am fine with the name change you propose.
> + especially if
> + there are a very large number of rows containing any single one of the
> + three keys
I suggest that you phrase this as "three index items".
> + A disadvantage of the <literal>jsonb_path_ops</literal> approach is
> + that it produces no index entries for JSON structures not containing
> + any values, such as <literal>{"a": {}}</literal>. If a search for
I suggest "any values or elements".
Even though I previously called hashing an implementation detail, we
are bound to have to mention it in passing when discussing the
limitations of jsonb_hash_ops/jsonb_path_ops. I think that you should
proceed with committing the entire patch, including the doc changes
that discuss implementation details around the two GIN opclasses.
--
Peter Geoghegan
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