This is possible now

They are still in the main branch in Filter.php class 🤔

Commented-out removeNullKeys left in production code

The removeNullKeys call was commented out, meaning MongoDB documents are now inserted with null-value keys stored explicitly:

//$record = $this->removeNullKeys($record);
$result = $this->insertDocument($name, $record, $options);

This is a significant behavioral change:

1. isNull() / isNotNull() queries may now match (or stop matching) documents that previously behaved differently — in MongoDB a stored null key is distinct from a missing key.
2. $exists / $notExists semantics are affected for the same reason.
3. Document size grows for every null-valued attribute in every newly inserted document.

This looks like debug code accidentally left in. If the intent is to stop stripping nulls, the line should be deleted (not commented out) with an explanatory comment. If it was accidentally removed, restore it:

getAttributeProjection() can return an empty string, producing invalid SQL

The method skips $collection selects but will return '' if all provided selects resolve to $collection:

$string = '';
foreach ($selects as $select) {
    if ($select->getAttribute() === '$collection') {
        continue; // all entries skipped
    }
    $string .= ...;
}
return $string; // '' when all selects were '$collection'

When called with [Query::select('$collection')], the generated SQL becomes SELECT FROM \table` AS `main` …— a syntax error that throws an unhandledPDOException. The validator permits select('$collection')via thevalidateAttributeExist` early-return, so this path is reachable by callers.

Add a fallback after the loop:

casting() silently drops all attributes not found in any collection schema

The rewritten casting() creates a brand-new Document and skips any key it cannot resolve against $internals or $schema:

$attribute = $internals[$key] ?? null;
if (is_null($attribute)) {
    $attribute = $schema[$collection->getId()][$this->adapter->filter($key)] ?? null;
}
if (is_null($attribute)) {
    continue; // silently dropped from the new document
}

The old implementation mutated the original document, preserving unknown keys. Because getSupportForCasting() is true for all SQL adapters, any runtime-injected attribute or join-sourced column that cannot be resolved through the select-alias lookup is now silently lost before decode() runs.

If this is intentional (all join columns are guaranteed to be matched via the $selects loop), please add a comment making that contract explicit and add a test that covers a column not present in any schema. Otherwise, consider preserving unresolved attributes similar to how decode() handles schemaless databases.

Misleading comment contradicts the actual code behaviour

$orders[] = Query::orderAsc(); // In joins we should not add a default order, we should validate when using a cursor we should have a unique order

The comment says joins should not get a default order, but Query::orderAsc() (which defaults to $sequence) is unconditionally added for all queries, including joins. Either:

• Remove the comment if a default $sequence order is intentional for joins too, or
• Guard with if (empty($joins)) so join queries behave differently, and document what cursor users must supply instead.

Commented-out class bodies should be deleted, not left as dead code

Both IndexedQueries.php and Queries/Documents.php now consist entirely of commented-out class bodies (148 and ~80 lines respectively). This creates confusion about whether these classes are still partially active, temporarily disabled, or permanently superseded.

If Queries/Queries.php is the permanent replacement, please delete these files so git history cleanly records the removal. If they need to stay temporarily, add a @deprecated docblock at the top of each file pointing to the replacement class.