[Firebird-devel] [FB-Tracker] Created: (CORE-5356) OVERLAY with binary blob - data corruption

[Karel R. (JIRA) <tr...@fi...>]

OVERLAY with binary blob - data corruption
------------------------------------------

                 Key: CORE-5356
                 URL: http://tracker.firebirdsql.org/browse/CORE-5356
             Project: Firebird Core
          Issue Type: Bug
          Components: Engine
    Affects Versions: 3.0.0
         Environment: Firebird 3.0.0 64bit, Windows 10 Pro 64 bit CZ
            Reporter: Karel Rys


Hello,

I have a table like this:

CREATE TABLE Users
(
...
 Prava           blob,
...
);

Records in this table now have char_length of Prava in range 399 to 403. It stores binary zeroes and ones (user rights in our application). 
When I run this:

SELECT
 char_length(a.Prava) as ActualLength,
 ascii_val(a.Prava) as NewValue1,
 ascii_val(substring(a.Prava FROM 1 FOR 1)) as NewValue2,
 ascii_val(OVERLAY(
  a.Prava PLACING ascii_char(1) FROM 200 for 1
 )) as NewValue3,
 ascii_val(substring(OVERLAY(
  a.Prava PLACING ascii_char(1) FROM 200 for 1
 ) FROM 1 FOR 1)) as NewValue4,
 a.*
FROM Users a

I get:

ActualLength, NewValue1, NewValue2, NewValue3, NewValue4, ...
403, 1, 1, 46, 46, ...
402, 1, 1, 1, 1, ...
399, 0, 0, 0, 0, ...
402, 1, 1, 1, 1, ...
...

It seems that OVERLAY returns wrong data for the first record - there should not be any "46". 

Kind regards,

Karel Rys



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