https://grasswiki.osgeo.org/w/index.php?action=history&feed=atom&title=SQLite_backend_vector_maps 2026-04-03T17:56:59Z Revision history for this page on the wiki MediaWiki 1.41.0 https://grasswiki.osgeo.org/w/index.php?title=SQLite_backend_vector_maps&diff=24086&oldid=prev 2017-04-03T15:52:11Z

<p>Extra tricks for power users</p> <p><b>New page</b></p><div>== Separate SQLite database files for vector maps ==<br /> <br /> IMPORTANT: Extra tricks for power users!<br /> <br /> Since SQLite does not support concurrent write access to its DB file ([https://sqlite.org/lockingv3.html reference]), '''parallelized vector map processing in a single mapset''' is hampered (&quot;Busy SQLite&quot; warnings).<br /> <br /> As a solution, instead of storing the vector attributes in a single SQLite database file in each mapset, individual SQLite files are to be created on a per-map basis. Simply running the next command will do the job to activate this behaviour. This can be run right after mapset creation:<br /> <br /> db.connect driver=sqlite database='$GISDBASE/$LOCATION_NAME/$MAPSET/vector/$MAP/sqlite.db'<br /> <br /> Most (all?) of the v.db.* commands work with vector map specific database files. The db.* commands seemed work as well, if the database path is provided at the command line.<br /> <br /> === Background info ===<br /> <br /> ''Remarks by Sören Gebbert:''<br /> <br /> I skipped the sqlite directory in the vector map path ($MAP/sqlite/sqlite.db -&gt; $MAP/sqlite.db), since this directory must be created when a new vector is opened, hence the vector-open-new functions must be modified to support a separate sqlite directory. With the simple solution the directory fsync() behavior of sqlite will force now all vector map specific files to be flushed to disc. This may be a performance problem.<br /> <br /> ''Hints (by Markus Metz):''<br /> <br /> SQLite might not open the (new) database at all if it can not fsync() the directory. That will not result in performance penalty but in a fatal error, therefore it is a good idea to keep the sqlite db in a separate folder.<br /> <br /> The GRASS &quot;sqlite&quot; driver attempts to create the sqlite directory (db__driver_open_database() in trunk/db/driver/sqlite/db.c) if the directory does not exist, therefore Vect_open_new*() should not need any modification.<br /> <br /> ===References===<br /> <br /> [https://lists.osgeo.org/pipermail/grass-dev/2016-September/082208.html Thread on GRASS-dev mailing list on the topic] (source of the information in this article)<br /> <br /> [[Category:FAQ]]<br /> [[Category:database]]<br /> [[Category:vector]]</div>

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