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@@ -141,8 +141,7 @@ The following vector objects are defined:
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- kernel: a 3D centroid in a volume;
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- volume: a 3D corpus, the topological composition of faces and kernel.
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-Note that all lines and boundaries can be polylines (with nodes in
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-between).
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+Note that all lines and boundaries can consist of multiple segments.
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Topology also holds information about isles. Isles are located within an area, not
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touching the boundaries of the outer area. Isles consist of one or more areas
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@@ -196,6 +195,7 @@ This directory contains these files:
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- <b>coor</b> - binary file, coordinates [former dig/ file]
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- <b>topo</b> - binary file, topology [former dig_plus/ file]
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+- <b>sidx</b> - binary file, spatial index
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- <b>cidx</b> - binary file, category index
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- <b>head</b> - text file, header information [former part of dig/ file]
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- <b>dbln</b> - text file, link(s) to attribute table(s)
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@@ -549,7 +549,7 @@ spatial index without topology.
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\section vlib_spidx Vector library spatial index management
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-Spatial index (based on R-tree) is generated on the fly.
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+Spatial index (based on R-tree) is created with topology.
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Spatial index occupies a lot of memory but it is necessary for
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topology building. Also, it takes a long time to release the memory
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@@ -563,6 +563,10 @@ By default the memory is not released.
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It is possible to call Vect_set_release_support() before Vect_close()
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to enforce memory release, but it takes a long time on large files.
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+The spatial index is stored in file and not loaded for old vectors that
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+are not updated, saving a lot of memory. Spatial queries are done in
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+file.
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+
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Currently most of the modules do not release the memory occupied for
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spatial index and work like this (pseudocode):
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@@ -594,14 +598,15 @@ int main
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but it takes longer.
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<P>
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-It make sense to release the spatial index if it is used only at the beginning
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-of a module or in permanently running programs like QGIS.
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+It makes sense to release the spatial index if it is used only at the beginning
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+of a module or in permanently running programs like QGIS. Note that this
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+applies only when creating a new vector or updating an old vector.
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For example:
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\code
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int main
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{
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- Vect_open_old();
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+ Vect_open_update();
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// select features using spatial index, e.g. Vect_select_lines_by_box()
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Vect_set_release_support();
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Vect_close(); // memory is released
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@@ -961,11 +966,15 @@ programming.
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- Vect_get_built()
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- - Vect_save_spatial_index()
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+ - Vect_build_sidx_from_topo()
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+
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+ - Vect_build_sidx()
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+
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+ - Vect_save_sidx()
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- Vect_save_topo()
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- - Vect_spatial_index_dump()
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+ - Vect_sidx_dump()
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- Vect_topo_dump()
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@@ -1410,7 +1419,7 @@ programming.
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- Vect_open_old_head()
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- - Vect_open_spatial_index()
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+ - Vect_open_sidx()
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- Vect_open_topo()
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@@ -1480,7 +1489,7 @@ programming.
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- Vect_rewind()
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-\section select Vector select functions
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+\section sindex Vector spatial index functions
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- Vect_select_areas_by_box()
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@@ -1495,11 +1504,7 @@ programming.
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- Vect_select_nodes_by_box()
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-\section sindex Vector spatial index functions
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-
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- - Vect_build_sidx_from_topo()
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-
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- - Vect_build_spatial_index()
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+\section select custom spatial index functions
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- Vect_spatial_index_add_item()
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Markus Metz