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<div class="gmail_quote">2010/8/7 Frank Warmerdam <span dir="ltr"><<a href="mailto:warmerdam@pobox.com">warmerdam@pobox.com</a>></span><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<br>
ogr2ogr has a -select switch to identify desired fields<br>
to be copied to the output. I imagine ogr2ogr could<br>
benefit from ignoring all the undesired attributes using<br>
this new api.<br></blockquote><div><br><br>Frank,<br><br>There are some other tools like ogrinfo, gdal_grid also support the sql option. I mean it would be desirable to provide unique implementation for each.<br> <br></div>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<br>
Currently there is no logic in the OGR SQL engine to<br>
ignore fields not needed in the result but I can see that<br>
adding this would be desirable. It would require some<br>
work to walk all the expression trees (for the WHERE<br>
and each of the column expressions) to identify the<br>
fields that are used in the primary and joined tables. I<br>
would potentially be willing to implement this optimization.<br>
<br></blockquote><div><br><br>In this case I would support to postpone the implementation in ogr2ogr to avoid parallel approaches to coexist in ogr2ogr and the common code.<br> <br></div></div>Best regards,<br><br>Tamas<br>
<br>