Database Reference
In-Depth Information
Figure 10-9.
Data access overhead comparison
Now that all the warnings are laid out, let's look at a scenario for which a shard makes sense and
probably improves both performance and scalability. Imagine a DOC table that contains only two
records. The table contains a few fields that represent document metadata, such as Title and Author ID.
However, this table also contains a large field: a
varbinary
column called Document that holds a PDF
file. Each PDF file is a few megabytes in size. Figure 10-10 shows the output of the table. Because this
database is loaded in SQL Azure, the
SELECT * FROM DOCS
statement returns a few megabytes of data on
an SSL encrypted link. The execution of this statement takes about 2.5 seconds on average, or roughly
1.25 seconds per record.
