`documentdb_api.find_and_modify` may not return data

[AlekSi]

Describe the bug

Environment

• Any OS
• Any architecture
• PostgreSQL 17.5
• DocumentDB 0.103

Reproduction Steps

test> db.coll.insertOne({v: 'x'.repeat(1939)});
{
  acknowledged: true,
  insertedId: ObjectId('6820a9109c3f60538a3b9274')
}
test> db.coll.findOneAndDelete({})
{ n: 1 }

test> db.coll2.insertOne({v: 'x'.repeat(1938)});
{
  acknowledged: true,
  insertedId: ObjectId('6820a92c9c3f60538a3b9275')
}
test> db.coll2.findOneAndDelete({})
{
  _id: ObjectId('6820a92c9c3f60538a3b9275'),
  v: 'xxx […] xxx'
}

Expected behavior

documentdb_api.find_and_modify returns data in both cases.

Actual behavior

When data is too large, this function does not return the data.

Additional context

See the FerretDB user bug report at FerretDB/FerretDB#5145 and our test script at FerretDB/FerretDB#5148.

[abinav2307]

@lichoil to review.

[lichoil]

@zinanren is working on this.

[omni-htg]

Thanks team, much appreciated!