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<div class="moz-cite-prefix">I confirm that the structure of the TAB
dataset uses 512 bytes data blocks organized in a tree structure,
so reading from the file implies lots of random access over the
whole file even if you read the features sequentially since a
single feature is stored in multiple data blocks of various types
(feature header blocks, feature coordinate blocks, etc.). It
would be interesting to know if VSI_CACHE as suggested by Even
will help.</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">Daniel<br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">On 2022-07-27 11:55, Even Rouault
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:98136954-c8ea-4586-686a-4cb99cfede7e@spatialys.com">
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<p>Moises,</p>
<p>I've not reviewed in depth the MITAB driver, but reading from a
.tab file may require random access, and it is thus not
surprising that reading from a compressed file may exhibit poor
performance. You might try to set the VSI_CACHE config option /
env variable to YES, but no guarantee this will help for your
use case.</p>
<p>Even<br>
</p>
<div class="moz-cite-prefix">Le 27/07/2022 Ã 11:39, Moises Calzado
via gdal-dev a écrit :<br>
</div>
<blockquote type="cite"
cite="mid:CAObRW4TKO05RkhMqVLXKa_PLH++6cs7rzWiXYVf-suU4XFcoZQ@mail.gmail.com">
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charset=UTF-8">
<div dir="ltr">
<div>Hi everyone!<br>
</div>
<div><br>
</div>
<div>We're using ogr2ogr to convert MapInfo TAB files into CSV
format using the following command:</div>
<div><br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">ogr2ogr -f CSV
-skipfailures -makevalid /vsistdout/ /vsizip/onLDU.zip  -oo
AUTODETECT_TYPE=YES -lco CREATE_CSVT=YES > test_2.csv</blockquote>
<div><br>
</div>
<div>The file weights ≈200 MB and the process is taking too
much time to finish (almost 20 min), so we don't know if
we're doing something wrong regarding the command that we
launch.</div>
<div>Â </div>
<img src="cid:part1.HlvVq6Ad.N1DqMV6E@mapgears.com"
alt="Screenshot 2022-07-20 at 12.55.14.png" class=""
width="542" height="41"><br>
<div>Â </div>
<div>However, if we launch the same command against the .tab
file instead of using the vsizip virtual file system, it
takes less than 30 seconds to complete.</div>
<div><br>
</div>
<div>Have you ever seen something like this? Do you know if
it's expected that it takes too much time to process this
kind of files, or we're doing something wrong?</div>
<div><br>
</div>
<div>Thanks so much for your help in advance,</div>
<div>Regards!</div>
-- <br>
<div dir="ltr" class="gmail_signature"
data-smartmail="gmail_signature"> <strong>Moises Calzado</strong>
<p style="margin-bottom:4px;margin-top:4px"> Support
Engineer </p>
<p style="margin-bottom:20px;margin-top:4px"> (US) +1 917
463 3232 | (ES) +34 911 165 823 | <a
href="mailto:mcalzado@carto.com" target="_blank"
moz-do-not-send="true" class="moz-txt-link-freetext">mcalzado@carto.com</a>
</p>
<a
href="https://spatial-data-science-conference.com/2022/newyork/"
rel="nofollow" target="_blank" moz-do-not-send="true"> <img
src="https://storage.googleapis.com/carto-it-files/signature/SDSC-2022-NY_Signature-mini.jpg"
moz-do-not-send="true" width="516.656px" height="50"> </a>
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<br>
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My software is free, but my time generally not.</pre>
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<pre class="moz-signature" cols="72">--
Daniel Morissette
Mapgears Inc
T: +1 418-696-5056 #201</pre>
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