On Jan 21, 2024, at 14:43, Tom Lane <t...@sss.pgh.pa.us> wrote: > I don't entirely buy this argument --- if that is the interpretation, > of what use are predicate check expressions? It seems to me that we > have to consider them as being a shorthand notation for filter > expressions, or else they simply do not make sense as jsonpath.
I believe it becomes pretty apparent when using jsonb_path_query(). The filter expression returns a set (using the previous \gset example): david=# select jsonb_path_query(:'json', '$.track.segments[*].HR ? (@ > 10)'); jsonb_path_query ------------------ 73 135 (2 rows) The predicate check returns a boolean: david=# select jsonb_path_query(:'json', '$.track.segments[*].HR > 10'); jsonb_path_query ------------------ true (1 row) This is the only way the different behaviors make sense to me. @? expects a set, not a boolean, sees there is an item in the set, so returns true: david=# select jsonb_path_query(:'json', '$.track.segments[*].HR > 1000'); jsonb_path_query ------------------ false (1 row) david=# select :'json'::jsonb @? '$.track.segments[*].HR > 1000'; ?column? ---------- t (1 row) Best, David
