Submitted by: @pavel-zotov

Currently documentation ( http://www.firebirdsql.org/refdocs/langrefupd25-intfunc-substring.html ) issues that "this function fully supports binary and text BLOBs of ___any___ length and character set" (note on emphasized "any").

This is false in case when there is text blob of length more than 2 Gb.
I've created such blob by fill GTT tables with result of

RECREATE SEQUENCE G;
RECREATE GLOBAL TEMPORARY TABLE GTT(BLOB_FLD BLOB) ON COMMIT DELETE ROWS;
SELECT LIST( gen_id( g, 1 ) ) FROM RDB$TYPES,RDB$TYPES,RDB$TYPES,(SELECT 1 k FROM RDB$TYPES ROWS 15);

-- and after that blob_fld will have length 2'346'948'497 bytes.

Exception:

Statement failed, SQLSTATE = 22003
arithmetic exception, numeric overflow, or string truncation
-numeric value is out of range

-- raises when trying to do:

select substring( bob_field from 2147483649 for 1); // NOTE: exception does NOT appear when 2nd arg = 2147483648, i.e. exact power(2, 31) from gtt;
select substring( bob_field from 2147483647 for 2147483648) from gtt;

It will be nice if we'll have new implementation of substring (and all other functions for string handling) that will be able to operate with blobs which length more than 2Gb.