Question about performance of dataset with large blobs in combination with deferredblobread

Discussion of open issues, suggestions and bugs regarding PgDAC (PostgreSQL Data Access Components) for Delphi, C++Builder, Lazarus (and FPC)
Post Reply
Hendrikse
Posts: 2
Joined: Fri 31 Aug 2018 11:40

Question about performance of dataset with large blobs in combination with deferredblobread

Post by Hendrikse » Mon 12 Nov 2018 14:24

I have a dataset which includes large blobfields. When fetching this data with a pgquery it takes a lot of time for the pgquery to open. While monitoring my network activity as the query was opening i noticed a rather high peak. It looks like all the data in the blobs is being retrieved from the server.

I noticed two properties that seem to affect this behaviour, DeferredBlobRead and CacheBlobs. The description of deferredblobread especially seems to describe the behaviour i would want, where blobfield data is only being retreived from the server once explicitely requested. When testing out these properties however, I noticed no change in the performance nor the network activity.

Am I right in thinking that deferredblobread = true should stop blobs being retreived from server in the pgquery.open? If so then am I using it wrong? I set the property on the the pgquery object before the open. If that's not what deferredblobread does is there some other way to do what I want to do?

azyk
Devart Team
Posts: 1119
Joined: Fri 11 Apr 2014 11:47
Location: Alpha Centauri A

Re: Question about performance of dataset with large blobs in combination with deferredblobread

Post by azyk » Tue 13 Nov 2018 06:56

Please use the contact form at our site: https://www.devart.com/company/contactform.html . Compose a small sample demonstrating how BLOB data is fetched. Send the sample to us. In the sample, include scripts for creating and generating test data. BLOBs content is not important. The BLOBs size you use is important.

Post Reply