Thank you Karl and David
Ideally as far as I can tell the index would need to be show_id, file_id,
lower(…)
The question is if this is possible ?
Thanks
Armand
> On Jun 1, 2017, at 12:24 PM, Karl Czajkowski <kar...@isi.edu> wrote:
>
> On May 31, armand pirvu modulated:
>
>> The idea is that I would like to avoid having an index for each key
>> possibly wanted to search, but rather say have the whole record then
>> search by the key and get the key value, thus having one index serving
>> multiple purposes so to speak
>>
>
> First, benchmarking would be important to figure out if any proposed
> indexing actually speeds up the kinds of queries you want to perform.
> With the recently added parallel query features, a simpler indexing
> scheme with some brute-force search might be adequate?
>
> But, you could use a search idiom like this:
>
> (lower(json_column::text)::json) -> lower('key') = 'value'::json
>
> This will down-convert the case on all values and keys. The left-hand
> parenthetic expression could be precomputed in an expression index to
> avoid repeated case conversion. But, typical searches will still have
> to scan the whole index to perform the projection and match the final
> value tests on the right-hand side.
>
> If you want to do things like substring matching on field values, you
> might stick with text and using regexp matches:
>
> (lower(json_column::text)) ~ 'valuepattern'
>
> or more structural searches:
>
> (lower(json_column::text)) ~ '"key": "[^"]*substring[^"]*"'
>
> Here, the left-hand expression could be trigram indexed to help with
> sparse, substring matching without a full index scan. We've had good
> luck using trigram indexing with regexp matching, though I've honestly
> never used it for the purpose sketched above...
>
> Karl
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