Port Bug Report: string concatenation operator association problem

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POSTGRESQL BUG REPORT TEMPLATE
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Your name : Leo Kim
Your email address : cocoja(at)sarang(dot)net

Category : runtime: back-end: SQL
Severity : non-critical

Summary: string concatenation operator association problem

System Configuration
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Operating System : FreeBSD 2.2.8

PostgreSQL version : 6.4

Compiler used : egcs 2.91.5

Hardware:
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Pentium II 300MHz, 128MB RAM

Versions of other tools:
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Problem Description:
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The string concatenation operator || doesn't have any associativity like + or -.
That is I can't use it as 'a' || 'b' || 'c' || 'd'.
I had to use parenthesis to get the result as (('a' || 'b') || 'c') || 'd'. I don't believe there should be a particular reason to deffer || operator from other binary operator. Is this a bug? Or any intention for it?

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Test Case:
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create table x (data text);
insert into x values ('a'||'b'||'c'||'d'); <- not working
insert into x values (((('a'||'b')||'c')||'d')); <- working

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Solution:
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