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From: Apache Wiki <wikidiffs@apache.org>
To: Apache Wiki <wikidiffs@apache.org>
Date: Sat, 19 Nov 2011 00:23:58 -0000
Message-ID: <20111119002358.83490.52107@eos.apache.org>
Subject: 
 =?utf-8?q?=5BSolr_Wiki=5D_Update_of_=22DIHCustomTransformer=22_by_Gustavo?=
 =?utf-8?q?Munoz?=
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The "DIHCustomTransformer" page has been changed by GustavoMunoz:
http://wiki.apache.org/solr/DIHCustomTransformer?action=3Ddiff&rev1=3D7&rev=
2=3D8

  =

  ----
  =3D=3D=3D What about returning values like null or an empty List? =3D=3D=
=3D
- Let TS =3D {t=C2=AB0=C2=BB, t=C2=AB1=C2=BB, t=C2=AB2=C2=BB, ..., t=C2=ABn=
=C2=BB} is the transformer (ordered) list configured for a particular entit=
y and say t=C2=ABi=C2=BB, with i <=3D n and i >=3D 0, returns null for a pa=
rticular row (or for all the rows that a previous Transformer that creates =
multiple rows from the original one), then there are two cases.
+ Let {{{TS =3D {t=C2=AB0=C2=BB, t=C2=AB1=C2=BB, t=C2=AB2=C2=BB, ..., t=C2=
=ABn=C2=BB} }}}be the transformer (ordered) list configured for a particula=
r entity and say {{{t=C2=ABi=C2=BB}}}, with {{{i <=3D n}}} and {{{i >=3D 0}=
}}, returns {{{null}}} for a particular row (or for all the rows that a pre=
vious Transformer that creates multiple rows from the original one), then t=
here are two cases.
- If no transformer t=C2=ABk=C2=BB, with k < i, returns a List of rows, the=
n that particular row is ignored, that means, it won't be inserted, deleted=
 or updated. Additionally no transformer t=C2=ABj=C2=BB, with j > i, will b=
e invoked.
+ If no transformer {{{t=C2=ABk=C2=BB}}}, with {{{k < i}}}, returns a {{{ja=
va.util.List}}} of rows, then that particular row is ignored, that means, i=
t won't be inserted, deleted or updated. Additionally no transformer {{{t=
=C2=ABj=C2=BB}}}, with {{{j > i}}}, will be invoked.
- If there is a transformer t=C2=ABk=C2=BB, with k < i, that returns a List=
 of rows for that particular row, an t=C2=ABi=C2=BB returns null for all th=
ose recently created rows, then a java.lang.!IndexOutBoundsException will b=
e thrown.
+ If there is a transformer {{{t=C2=ABk=C2=BB}}}, with {{{k < i}}}, that re=
turns a {{{java.util.List}}} of rows for that particular row, and {{{t=C2=
=ABi=C2=BB}}} returns {{{null}}} for all those recently created rows, then =
a {{{ java.lang.IndexOutBoundsException }}} will be thrown.
  =

- Now, if at any time a transformRow call returns an empty List, a java.lan=
g.!IndexOutBoundsException will be thrown.
+ Now, if at any time a transformRow call returns an empty {{{java.util.Lis=
t}}}, a {{{ java.lang.IndexOutBoundsException }}} will be thrown. So you sh=
ould never return an empty {{{java.util.List}}}.
  ----
  =3D=3D A General TrimTransformer =3D=3D
  Suppose you want to write a general !TrimTransformer without hardcoding t=
he column on which it needs to operate. Now we'd need to have a flag on the=
 field in data-config.xml to indicate that the !TrimTransformer should appl=
y itself on this field.