Vfp nolock when updating sql
With execution plan collection disabled, all required pages in the buffer pool, and no resetting of the end date values between runs, this query typically executes in around 5700ms on my laptop.
The statistics IO output is as follows: (read ahead reads and LOB counters were zero, and are omitted for space reasons) The scan count represents the number of times a scanning operation was started.
As before, the lack of a breakdown makes it impossible to determine which iterator (of the two Scans and the Update) was responsible for the 3 million reads.
Nevertheless, I can tell you that the Clustered Index Scans count only a few thousand logical reads each.
This article uses a simple query to explore some deep internals concerning update queries.The statistics IO output is: This shows two scans started for the Example table (one for each Clustered Index Scan iterator).The logical reads are again an aggregate over all iterators that access this table in the query plan.To focus on the maximum performance potential of this execution plan, we can run the same update query multiple times.Clearly, only the first run will result in any changes to the data, but this turns out to be a minor consideration.