[core] Fix snapshots table failing IN filter for unknown id

[ArnavBalyan]

Purpose

• snapshot_id in (...) statement fails when the in clause is supplied with a non existent snapshot id.
• This is because the query reads files for each input id without checking for file presence.
• If expired id is supplied, the query throws because snapshot manager is not checking if the snapshot exists.
• Fix by adding filter.

Tests

• UT

[JingsongLi]

While IN (existing, missing) skips non-existent snapshots or schemas, the case where snapshot_id = missing is still hardcoded in new tests to throw an exception; this creates inconsistent predicate semantics for the same system table, whereas returning an empty set for non-existent IDs would be more logical for SQL queries. Additionally, the exists → read flow remains susceptible to a TOCTOU (Time-of-Check to Time-of-Use) race condition involving snapshot expiration.

[ArnavBalyan]

While IN (existing, missing) skips non-existent snapshots or schemas, the case where snapshot_id = missing is still hardcoded in new tests to throw an exception; this creates inconsistent predicate semantics for the same system table, whereas returning an empty set for non-existent IDs would be more logical for SQL queries. Additionally, the exists → read flow remains susceptible to a TOCTOU (Time-of-Check to Time-of-Use) race condition involving snapshot expiration.

Hi @JingsongLi thanks for review, have updated the equality semantics to match IN filter, both do not fail on invalid snapshot ids, also fixed the TOCTOU concern. Thanks!