Hi,I want to ask a question about json index.Can I make a index on a field of a json column?e.g, for table 'json_tab' you given, can I run something like "create index 'json_index' on json_tab::key"?
Yes.
Here it is an example: http://stackoverflow.com/questions/17807030/how-to-create-index-on-json-field-in-postgres-9-3
Also, in 9.4 we got JSONB data type, which may enhance JSON fields performance.
