When working with custom code that manipulates lists that contain a large number of fields, the ULS logs will likely be littered with the following entries:
A large block of literal text was sent to sql. This can result in blocking in sql and excessive memory use on the front end. Verify that no binary parameters are being passed as literals, and consider breaking up batches into smaller components. If this request is for a SharePoint list or list item, you may be able to resolve this by reducing the number of fields.
followed by:
Slow Query Duration: [time in milliseconds]
then:
Slow Query StackTrace-Managed: [complete stack trace]
Note: This one’s important as you can look at the stack and identify the exact area of code that initiates the slow query log entries.
and finally:
SqlCommand: [SQL statement responsible for the log entry]
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