From: Achilleas Mantzios <achill@matrix.gatewaynet.com>
Organization: Dynacom Tankers Mgmt
To: pgsql-sql@postgresql.org
Subject: Re: can someone explain confusing array indexing nomenclature
Date: Tue, 20 Feb 2007 09:42:17 +0200
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References: <8971770.post@talk.nabble.com>
	<200702161034.43399.achill@matrix.gatewaynet.com>
	<9009934.post@talk.nabble.com>
In-Reply-To: <9009934.post@talk.nabble.com>
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=CE=A3=CF=84=CE=B9=CF=82 =CE=A0=CE=B1=CF=81=CE=B1=CF=83=CE=BA=CE=B5=CF=85=
=CE=AE 16 =CE=A6=CE=B5=CE=B2=CF=81=CE=BF=CF=85=CE=AC=CF=81=CE=B9=CE=BF=CF=
=82 2007 20:35, =CE=BF/=CE=B7 chrisj =CE=AD=CE=B3=CF=81=CE=B1=CF=88=CE=B5:
> I am quite sure the [2] is not discarded, easy enough to test but I don't
> have access to PG at the moment.

Well it should, since

dynacom=3D# SELECT=20
(CAST( '{{meeting,lunch},{training,presentation}}' as text[][]))[1:1];
       text
=2D------------------
 {{meeting,lunch}}
(1 row)

dynacom=3D# SELECT=20
(CAST( '{{meeting,lunch},{training,presentation}}' as text[][]))[1:1][1];
    text
=2D------------
 {{meeting}}
(1 row)

dynacom=3D# SELECT=20
(CAST( '{{meeting,lunch},{training,presentation}}' as text[][]))[1:1][2];
       text
=2D------------------
 {{meeting,lunch}}
(1 row)

dynacom=3D# SELECT=20
(CAST( '{{meeting,lunch},{training,presentation}}' as text[][]))[1:1][3];
       text
=2D------------------
 {{meeting,lunch}}
(1 row)

dynacom=3D# SELECT=20
(CAST( '{{meeting,lunch},{training,presentation}}' as text[][]))[1:1][1000];
       text
=2D------------------
 {{meeting,lunch}}
(1 row)

dynacom=3D#                           =20

>
> Achilleas Mantzios wrote:
> > =CE=A3=CF=84=CE=B9=CF=82 =CE=A0=CE=AD=CE=BC=CF=80=CF=84=CE=B7 15 =CE=A6=
=CE=B5=CE=B2=CF=81=CE=BF=CF=85=CE=AC=CF=81=CE=B9=CE=BF=CF=82 2007 18:55, =
=CE=BF/=CE=B7 chrisj =CE=AD=CE=B3=CF=81=CE=B1=CF=88=CE=B5:
> >> Thanks Achilleas,
> >>
> >> I see what you are saying, but if we consider just the index "[2]" for=
 a
> >> moment,
> >> it means something different depending upon the context  (in one case =
it
> >> means "2" and in the other case it means "1:2") and the context is
> >> determined by the format of indexes on other dimensions.
> >>
> >> I believe I understand....but incredibly confusing.
> >
> > Now that i think about it again, i speculate that the [2] is discarded.
> >
> >> - chris
> >>
> >> Achilleas Mantzios wrote:
> >> > =CE=9E=C2=A3=CE=9F=C2=84=CE=9E=CE=89=CE=9F=C2=82 =CE=9E=EF=BF=BD=CE=
=9E=CE=85=CE=9F=C2=84=CE=9E=C2=AC=CE=9F=C2=81=CE=9F=C2=84=CE=9E=C2=B7 14 =
=CE=9E=C2=A6=CE=9E=CE=85=CE=9E=C2=B2=CE=9F=C2=81=CE=9E=CE=8F=CE=9F=C2=85=CE=
=9E=C2=AC=CE=9F=C2=81=CE=9E=CE=89=CE=9E=CE=8F=CE=9F=C2=82 2007 21:31, =CE=
=9E=CE=8F/=CE=9E=C2=B7
> >>
> >> chrisj
> >
> > =CE=9E=C2=AD=CE=9E=C2=B3=CE=9F=C2=81=CE=9E=C2=B1=CE=9F=C2=88=CE=9E=CE=
=85:
> >> >> given the following table:
> >> >>
> >> >> protocal2=3D> select * from sal_emp ;
> >> >>  name  |      pay_by_quarter       |                 schedule
> >>
> >> -------+---------------------------+----------------------------------=
=2D-
> >>
> >> >>--- ---- Bill  | {10000,10000,10000,10000} |
> >> >> {{meeting,lunch},{training,presentation}}
> >> >>  Carol | {20000,25000,25000,25000} |
> >> >> {{breakfast,consulting},{meeting,lunch}}
> >> >> (2 rows)
> >> >>
> >> >> why do the following two queries yield different results??
> >> >>
> >> >> protocal2=3D> SELECT schedule[1][2] FROM sal_emp WHERE name =3D 'Bi=
ll';
> >> >>  schedule
> >> >> ----------
> >> >>  lunch
> >> >> (1 row)
> >> >>
> >> >> protocal2=3D> SELECT schedule[1:1][2] FROM sal_emp WHERE name =3D '=
Bill';
> >> >>      schedule
> >> >> -------------------
> >> >>  {{meeting,lunch}}
> >> >> (1 row)
> >> >
> >> > The [n:m] notation denotes a slice of the array (not element).
> >> > So schedule[1][2] is the Array element on 2nd col of 1st row,
> >> > while schedule[1:1][2] could mean
> >> > the second row of the subarray schedule[1:1][1:2].
> >> > So these two are foundamentally different things.
> >> > In my 7.4 even if you gave
> >> > SELECT schedule[1:1][888] FROM sal_emp WHERE name =3D 'Bill';
> >> > you would still get  {{meeting,lunch}} as a result.
> >> > (Right or wrong is another story).
> >> > Anyway the first time you query for a "text",
> >> > the second time you query for a "text[]", so you should expect
> >> > different results.
> >> > --
> >> > Achilleas Mantzios
> >> >
> >> > ---------------------------(end of
> >>
> >> broadcast)---------------------------
> >>
> >> > TIP 3: Have you checked our extensive FAQ?
> >> >
> >> >                http://www.postgresql.org/docs/faq
> >
> > --
> > Achilleas Mantzios
> >
> > ---------------------------(end of broadcast)---------------------------
> > TIP 3: Have you checked our extensive FAQ?
> >
> >                http://www.postgresql.org/docs/faq

=2D-=20
Achilleas Mantzios