Today I noticed strange behaviour, consider the following test:
postgres@126111=#create table foo ( a text );
CREATE TABLE
postgres@126111=#insert into foo values ( repeat('PostgreSQL is the world''s best database and leading by an Open Source Community.', 8000));
INSERT 0 1
postgres@126111=#select substring(a from 639921 for 81) from foo;
substring
-----------
(1 row)
Before below commit:
postgres@75761=#select substring(a from 639921 for 81) from foo;
substring
----------------------------------------------------------------------------------
PostgreSQL is the world's best database and leading by an Open Source Community.
(1 row)