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In developer's FAQ, update list API, from Tom Lane.

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Bruce Momjian
2007-05-05 10:21:13 +00:00
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doc/src/FAQ/FAQ_DEV.html
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@ -13,7 +13,7 @@
<H1>Developer's Frequently Asked Questions (FAQ) for
PostgreSQL</H1>
<P>Last updated: Sat May 5 00:09:15 EDT 2007</P>
<P>Last updated: Sat May 5 06:20:41 EDT 2007</P>
<P>Current maintainer: Bruce Momjian (<A href=
"mailto:bruce@momjian.us">bruce@momjian.us</A>)<BR>
@ -863,24 +863,25 @@
<DL>
<DT>lfirst(i), lfirst_int(i), lfirst_oid(i)</DT>
<DD>return the data (a point, integer and OID respectively) at
list element <I>i.</I></DD>
<DD>return the data (a pointer, integer or OID respectively) of
list cell <I>i.</I></DD>
<DT>lnext(i)</DT>
<DD>return the next list element after <I>i.</I></DD>
<DD>return the next list cell after <I>i.</I></DD>
<DT>foreach(i, list)</DT>
<DD>
loop through <I>list,</I> assigning each list element to
<I>i.</I> It is important to note that <I>i</I> is a List *,
loop through <I>list,</I> assigning each list cell to
<I>i.</I> It is important to note that <I>i</I> is a ListCell *,
not the data in the <I>List</I> element. You need to use
<I>lfirst(i)</I> to get at the data. Here is a typical code
snippet that loops through a List containing <I>Var *'s</I>
and processes each one:
<PRE>
<CODE> List *list;
<CODE>
List *list;
ListCell *i;
foreach(i, list)
@ -900,26 +901,26 @@
<DT>lappend(list, node)</DT>
<DD>add <I>node</I> to the end of <I>list.</I> This is more
expensive that lcons.</DD>
<DD>add <I>node</I> to the end of <I>list.</I></DD>
<DT>nconc(list1, list2)</DT>
<DT>list_concat(list1, list2)</DT>
<DD>Concat <I>list2</I> on to the end of <I>list1.</I></DD>
<DD>Concatenate <I>list2</I> on to the end of <I>list1.</I></DD>
<DT>length(list)</DT>
<DT>list_length(list)</DT>
<DD>return the length of the <I>list.</I></DD>
<DT>nth(i, list)</DT>
<DT>list_nth(list, i)</DT>
<DD>return the <I>i</I>'th element in <I>list.</I></DD>
<DD>return the <I>i</I>'th element in <I>list,</I>
counting from zero.</DD>
<DT>lconsi, ...</DT>
<DT>lcons_int, ...</DT>
<DD>There are integer versions of these: <I>lconsi,
lappendi</I>, etc. Also versions for OID lists: <I>lconso,
lappendo</I>, etc.</DD>
<DD>There are integer versions of these: <I>lcons_int,
lappend_int</I>, etc. Also versions for OID lists: <I>lcons_oid,
lappend_oid</I>, etc.</DD>
</DL>
</BLOCKQUOTE>
You can print nodes easily inside <I>gdb.</I> First, to disable
@ -944,7 +945,7 @@
<H3 id="item2.4">2.4) I just added a field to a structure.
What else should I do?</H3>
<P>The structures passing around from the parser, rewrite,
<P>The structures passed around in the parser, rewriter,
optimizer, and executor require quite a bit of support. Most
structures have support routines in <I>src/backend/nodes</I> used
to create, copy, read, and output those structures (in particular,