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table: docs: fix typos and grammar.
Author: Justin Pryzby Discussion: https://postgr.es/m/20190404055138.GA24864@telsasoft.com
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@ -587,7 +587,7 @@
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The catalog <structname>pg_am</structname> stores information about
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relation access methods. There is one row for each access method supported
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by the system.
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Currently, only table and indexes have access methods. The requirements for table
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Currently, only tables and indexes have access methods. The requirements for table
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and index access methods are discussed in detail in <xref linkend="tableam"/> and
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<xref linkend="indexam"/> respectively.
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</para>
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@ -106,11 +106,11 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
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</para>
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<para>
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In contrast to <command>CREATE TABLE AS</command> <command>SELECT
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In contrast to <command>CREATE TABLE AS</command>, <command>SELECT
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INTO</command> does not allow to specify properties like a table's access
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method with <xref linkend="sql-createtable-method" /> or the table's
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tablespace with <xref linkend="sql-createtable-tablespace" />. Use <xref
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linkend="sql-createtableas"/> if necessary. Therefore the default table
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linkend="sql-createtableas"/> if necessary. Therefore, the default table
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access method is chosen for the new table. See <xref
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linkend="guc-default-table-access-method"/> for more information.
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</para>
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@ -189,11 +189,11 @@ there.
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</para>
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<para>
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Note that the following sections describe the way the builtin
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Note that the following sections describe the behavior of the builtin
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<literal>heap</literal> <link linkend="tableam">table access method</link>,
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and the builtin <link linkend="indexam">index access methods</link> work. Due
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to the extensible nature of <productname>PostgreSQL</productname> other types
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of access method might work similar or not.
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and the builtin <link linkend="indexam">index access methods</link>. Due
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to the extensible nature of <productname>PostgreSQL</productname>, other
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access methods might work differently.
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</para>
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<para>
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@ -703,11 +703,11 @@ erased (they will be recreated automatically as needed).
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This section provides an overview of the page format used within
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<productname>PostgreSQL</productname> tables and indexes.<footnote>
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<para>
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Actually, neither table nor index access methods need not use this page
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format. All the existing index methods do use this basic format, but the
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data kept on index metapages usually doesn't follow the item layout
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rules. The <literal>heap</literal> table access method also always uses
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this format.
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Actually, use of this page format is not required for either table or
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index access methods. The <literal>heap</literal> table access method
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always uses this format. All the existing index methods also use the
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basic format, but the data kept on index metapages usually doesn't follow
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the item layout rules.
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</para>
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</footnote>
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Sequences and <acronym>TOAST</acronym> tables are formatted just like a regular table.
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@ -48,33 +48,33 @@
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callbacks and their behavior is defined in the
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<structname>TableAmRoutine</structname> structure (with comments inside the
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struct defining the requirements for callbacks). Most callbacks have
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wrapper functions, which are documented for the point of view of a user,
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rather than an implementor, of the table access method. For details,
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wrapper functions, which are documented from the point of view of a user
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(rather than an implementor) of the table access method. For details,
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please refer to the <ulink url="https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/include/access/tableam.h;hb=HEAD">
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<filename>src/include/access/tableam.h</filename></ulink> file.
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</para>
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<para>
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To implement a access method, an implementor will typically need to
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implement a AM specific type of tuple table slot (see
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To implement an access method, an implementor will typically need to
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implement an AM-specific type of tuple table slot (see
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<ulink url="https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/include/executor/tuptable.h;hb=HEAD">
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<filename>src/include/executor/tuptable.h</filename></ulink>) which allows
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<filename>src/include/executor/tuptable.h</filename></ulink>), which allows
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code outside the access method to hold references to tuples of the AM, and
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to access the columns of the tuple.
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</para>
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<para>
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Currently the the way an AM actually stores data is fairly
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unconstrained. It is e.g. possible to use postgres' shared buffer cache,
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but not required. In case shared buffers are used, it likely makes to
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postgres' standard page layout described in <xref
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linkend="storage-page-layout"/>.
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Currently, the way an AM actually stores data is fairly unconstrained. For
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example, it's possible, but not required, to use postgres' shared buffer
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cache. In case it is used, it likely makes sense to use
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<productname>PostgreSQL</productname>'s standard page layout as described in
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<xref linkend="storage-page-layout"/>.
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</para>
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<para>
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One fairly large constraint of the table access method API is that,
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currently, if the AM wants to support modifications and/or indexes, it is
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necessary that each tuple has a tuple identifier (<acronym>TID</acronym>)
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necessary for each tuple to have a tuple identifier (<acronym>TID</acronym>)
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consisting of a block number and an item number (see also <xref
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linkend="storage-page-layout"/>). It is not strictly necessary that the
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sub-parts of <acronym>TIDs</acronym> have the same meaning they e.g. have
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@ -83,13 +83,14 @@
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</para>
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<para>
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For crash safety an AM can use postgres' <link
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linkend="wal"><acronym>WAL</acronym></link>, or a custom approach can be
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implemented. If <acronym>WAL</acronym> is chosen, either <link
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linkend="generic-wal">Generic WAL Records</link> can be used — which
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implies higher WAL volume but is easy, or a new type of
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<acronym>WAL</acronym> records can be implemented — but that
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currently requires modifications of core code (namely modifying
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For crash safety, an AM can use postgres' <link
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linkend="wal"><acronym>WAL</acronym></link>, or a custom implementation.
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If <acronym>WAL</acronym> is chosen, either <link
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linkend="generic-wal">Generic WAL Records</link> can be used,
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or a new type of <acronym>WAL</acronym> records can be implemented.
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Generic WAL Records are easy, but imply higher WAL volume.
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Implementation of a new type of WAL record
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currently requires modifications to core code (specifically,
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<filename>src/include/access/rmgrlist.h</filename>).
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</para>
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@ -103,8 +104,8 @@
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<para>
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Any developer of a new <literal>table access method</literal> can refer to
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the existing <literal>heap</literal> implementation present in
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<filename>src/backend/heap/heapam_handler.c</filename> for more details of
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how it is implemented.
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<filename>src/backend/heap/heapam_handler.c</filename> for details of
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its implementation.
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</para>
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</chapter>
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