<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >Limitations</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REV="MADE" HREF="mailto:pgsql-docs@postgresql.org"><LINK REL="HOME" TITLE="PostgreSQL 8.0.11 Documentation" HREF="index.html"><LINK REL="UP" TITLE="GiST Indexes" HREF="gist.html"><LINK REL="PREVIOUS" TITLE="Implementation" HREF="implementation.html"><LINK REL="NEXT" TITLE="Examples" HREF="examples.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="stylesheet.css"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"><META NAME="creation" CONTENT="2007-02-02T03:57:22"></HEAD ><BODY CLASS="SECT1" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="5" ALIGN="center" VALIGN="bottom" >PostgreSQL 8.0.11 Documentation</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="implementation.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="gist.html" >Fast Backward</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" >Chapter 48. GiST Indexes</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="top" ><A HREF="gist.html" >Fast Forward</A ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="top" ><A HREF="examples.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="LIMITATIONS" >48.4. Limitations</A ></H1 ><P > The current implementation of <ACRONYM CLASS="ACRONYM" >GiST</ACRONYM > within <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN > has some major limitations: <ACRONYM CLASS="ACRONYM" >GiST</ACRONYM > access is not concurrent; the <ACRONYM CLASS="ACRONYM" >GiST</ACRONYM > interface doesn't allow the development of certain data types, such as digital trees (see papers by Aoki et al); and there is not yet any support for write-ahead logging of updates in <ACRONYM CLASS="ACRONYM" >GiST</ACRONYM > indexes. </P ><P > Solutions to the concurrency problems appear in Marcel Kornacker's thesis; however these ideas have not yet been put into practice in the <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN > implementation. </P ><P > The lack of write-ahead logging is just a small matter of programming, but since it isn't done yet, a crash could render a <ACRONYM CLASS="ACRONYM" >GiST</ACRONYM > index inconsistent, forcing a REINDEX. </P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="implementation.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="examples.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Implementation</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="gist.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Examples</TD ></TR ></TABLE ></DIV ></BODY ></HTML >