Hi,

I found that the subtype of JSON will be lost when the query uses an index.

This test case can reproduce this:

CREATE TABLE t(a INTEGER, j TEXT);
INSERT INTO t VALUES(1,'{"a":1}'),(2,'{"a":2}');
CREATE INDEX i_case ON t(CASE WHEN a>0 THEN json(j) END);

SELECT subtype(CASE WHEN a>0 THEN json(j) END) FROM t NOT INDEXED WHERE a=2;
SELECT subtype(CASE WHEN a>0 THEN json(j) END) FROM t INDEXED BY i_case WHERE a=2;

This is the output:

╭──────────────────────╮
│ subtype(CASE WHEN... │
╞══════════════════════╡
│                   74 │
╰──────────────────────╯
╭──────────────────────╮
│ subtype(CASE WHEN... │
╞══════════════════════╡
│                    0 │
╰──────────────────────╯

I can reproduce this with the trunk version 83d3a0d39b.