</para>

<para>

Tuple deforming is the process of transforming an on-disk tuple (see <xref

linkend="heaptuple"/>) into its in-memory representation. It can be

accelerated by creating a function specific to the table layout and the

number of columns to be extracted.

linkend="storage-tuple-layout"/>) into its in-memory representation.

It can beaccelerated by creating a function specific to the table layout

and thenumber of columns to be extracted.

</para>

</sect2>

<filename>src/include/storage/bufpage.h</filename>.

</para>

<para id="heaptuple">

<para>

Following the page header are item identifiers

(<type>ItemIdData</type>), each requiring four bytes.

An item identifier contains a byte-offset to

<para>

The final section is the <quote>special section</quote> which can

contain anything the access method wishes to store. For example,

contain anything the access method wishes to store. For example,

b-tree indexes store links to the page's left and right siblings,

as well as some other data relevant to the index structure.

Ordinary tables do not use a special section at all (indicated by setting

<structfield>pd_special</structfield> to equal the page size).

</para>

<sect2 id="storage-tuple-layout">

<title>Table Row Layout</title>

<para>

All table rows are structured in the same way. There is a fixed-size

it might be compressed, too (see <xref linkend="storage-toast"/>).

</para>

</sect2>

</sect1>

</chapter>