How does comparing BLOB fields work?

Posted by jquerijero on 22-Dec-2017 09:40

What exactly is being compared when it comes to comparing BLOB fields using = sign? I am comparing two BLOB fields that contain data for bitmaps and getting false match for some of my bitmaps.

All Replies

Posted by Fernando Souza on 22-Dec-2017 11:05

Comparison is done by looking at the bytes on both blobs. If the data is really not the same and it is giving you that they match, and you can reproduce it, please open a call with Technical Support.

Posted by jbijker on 09-Jan-2018 02:44

Is the BLOB field living on a DB field? If so you first need to COPY-LOB it to a longchar or whatever other variable because ABL won't fetch the BLOB data using a normal FIND. COPY-LOB will go and fetch the BLOB properly from the DB into memory.

Posted by gus bjorklund on 10-Jan-2018 08:58

may be a bug here.

As a (big) performance optimization, LOB value fetches are delayed until the LOB value is used. A reference to the LOB field should trigger a fetch if it has not already been fetched.

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