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

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Developer's Frequently Asked Questions (FAQ) for PostgreSQL
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Last updated: Sat May 5 00:09:15 EDT 2007
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Last updated: Sat May 5 06:20:41 EDT 2007
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Current maintainer: Bruce Momjian (bruce@momjian.us)
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Here are some of the List manipulation commands:
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lfirst(i), lfirst_int(i), lfirst_oid(i)
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return the data (a point, integer and OID respectively) at list
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element i.
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return the data (a pointer, integer or OID respectively) of
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list cell i.
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lnext(i)
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return the next list element after i.
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return the next list cell after i.
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foreach(i, list)
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loop through list, assigning each list element to i. It is
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important to note that i is a List *, not the data in the List
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element. You need to use lfirst(i) to get at the data. Here is
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a typical code snippet that loops through a List containing Var
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*'s and processes each one:
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loop through list, assigning each list cell to i. It is
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important to note that i is a ListCell *, not the data in the
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List element. You need to use lfirst(i) to get at the data.
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Here is a typical code snippet that loops through a List
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containing Var *'s and processes each one:
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List *list;
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List *list;
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ListCell *i;
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foreach(i, list)
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if list is NIL.
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lappend(list, node)
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add node to the end of list. This is more expensive that lcons.
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add node to the end of list.
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nconc(list1, list2)
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Concat list2 on to the end of list1.
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list_concat(list1, list2)
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Concatenate list2 on to the end of list1.
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length(list)
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list_length(list)
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return the length of the list.
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nth(i, list)
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return the i'th element in list.
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list_nth(list, i)
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return the i'th element in list, counting from zero.
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lconsi, ...
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There are integer versions of these: lconsi, lappendi, etc.
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Also versions for OID lists: lconso, lappendo, etc.
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lcons_int, ...
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There are integer versions of these: lcons_int, lappend_int,
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etc. Also versions for OID lists: lcons_oid, lappend_oid, etc.
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You can print nodes easily inside gdb. First, to disable output
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truncation when you use the gdb print command:
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2.4) I just added a field to a structure. What else should I do?
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The structures passing around from the parser, rewrite, optimizer, and
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The structures passed around in the parser, rewriter, optimizer, and
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executor require quite a bit of support. Most structures have support
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routines in src/backend/nodes used to create, copy, read, and output
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those structures (in particular, the files copyfuncs.c and

‎doc/src/FAQ/FAQ_DEV.html

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

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