Possible bug: SqlDataReader.ReadAsync hangs and produces high garbage collection.

Tested on: System.Data.SqlClient versions “4.4.0”, “4.8.0” and “4.8.1”

I’m trying to read from a table which has 8 records. In ReadAsync it fetches the first 6 records quickly and hangs around 45 seconds to fetch the rest 2. During that 45 seconds time produces very high garbage collection.

The synchronous version on the other hand fetches the records immediately and there is no visible garbage collection.

while (await reader.ReadAsync(cancellationToken).ConfigureAwait(false))
{
...
}

vs.

while (reader.Read())
{
...
}

[Wraith2]

That’s huge. Unless you actually need that as a string I strongly suggest using the GetTextReader overload in sequential mode, it’ll save you a lot of GC work.

[Wraith2]

Investigation stalled because there isn’t a complete repo, see “Can’t provide the db schema now.” above. If you have a self contained repo we can run then it can continue. Looking back at the report though It smells like long async strings to me and the answer is to not do that, fetch the string sync or use a textreader stream.