Why is performance so slow reading binary data from a SQL Azure DB with EF6.x

Question

I'm running a WPF client that hits a SQL Azure DB using EF 6.x. For the most part, everything seems to be working fine. The one exception is when I try to read a large binary column.
I am storing files in the DB as a binary column.  When I test using the local DB, everything sings.  When I switch to the Azure DB, I get timeouts when I try to read the file contents.  I have no problem saving the binary data to the DB, just
reading it.
I don't know how to troubleshoot this.  I looked at the Query Performance page in the Azure portal, but it doesn't time stamp anything in there and you can't clear it, so I can't correlate what's running with the queries that show up there.
I tried to start SQL profiler against the DB, but was denied because I'm not a member of the sysadmin fixed server role.
If I query for the data directly, it comes back quickly.  So this seems to be an Azure via EF issue.
Any help is appreciated.
http://digitalcamel.blogspot.com/

Answer 1

Hi Digital Camel,
Since I don't know what your scenario is, I won't argue too much about not storing binaries in your SQL DB, but still: don't store binaries in your SQL DB :). The main reason is simple: first and foremost, in both the current and future pricing tier your
levels are defines on the size of the DB. Basically, you pay way more by storing your binaries on your SQL layer rathern than storing them elsewhere, such as Azure Storage. Second, the protocol your binaries would be downloaded over the wire is prone to network
connectivity issues: you could use HTTP(S) or FTP instead, if you'd use Azure Storage. Last but not least, when you download the binary from your DB, you keep a connection open which in the end is a connection other users might have used to query data instead.
However, in regard to your question, how did you "query for the data directly"? Did you try to query the data using SSMS with the Client Statistics option on? This could tell you if the problem is network, server or client related.
Hope this helps!
Alex