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add ability to read geometries stored as TWKB directly (experimental)

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See TWKB-HOWTO.md for how to prepare data.

XML style parameters :

```xml
<Parameter name="twkb_encoding">True</Parameter>
<Parameter name="twkb_direct">True</Parameter>
```
This commit is contained in:
artemp 2016-03-22 10:30:04 +01:00
parent 0fb587875e
commit 186c80ca38
3 changed files with 90 additions and 33 deletions
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26
TWKB-HOWTO.md Normal file
View file

@ -0,0 +1,26 @@
### Direct TWKB
#### Prerequisites
* Standard set of planet OSM tables imported into PostgreSQL with `osm2pgsql` or similar.
#### Creating and populating TWKB table
```sql
create table planet_osm_polygon_twkb as (select * from planet_osm_polygon);
alter table planet_osm_polygon_twkb add column twkb bytea;
update planet_osm_polygon_twkb set twkb = ST_AsTWKB(way, 2);
alter table planet_osm_polygon_twkb drop column way;
```
#### Spatial index
```sql
create index planet_osm_polygon_twkb_index on planet_osm_polygon_twkb using GIST(ST_GeomFromTWKB(twkb));
```
##### Vacuum to update stats
```sql
VACUUM FULL ANALYZE VERBOSE planet_osm_polygon_twkb ;
\d+
```

96
plugins/input/postgis/postgis_datasource.cpp
View file

@ -89,6 +89,7 @@ postgis_datasource::postgis_datasource(parameters const& params)
max_async_connections_(*params_.get<mapnik::value_integer>("max_async_connection", 1)),
asynchronous_request_(false),
twkb_encoding_(false),
twkb_direct_(*params_.get<mapnik::boolean_type>("twkb_direct", false)),
twkb_rounding_adjustment_(*params_.get<mapnik::value_double>("twkb_rounding_adjustment", 0.0)),
simplify_snap_ratio_(*params_.get<mapnik::value_double>("simplify_snap_ratio", 1.0/40.0)),
// 1/20 of pixel seems to be a good compromise to avoid
@ -242,8 +243,14 @@ postgis_datasource::postgis_datasource(parameters const& params)
if (!geometryColumn_.empty() && srid_ <= 0)
{
std::ostringstream s;
s << "SELECT ST_SRID(\"" << geometryColumn_ << "\") AS srid FROM ";
if (twkb_direct_)
{
s << "SELECT ST_SRID(ST_GeomFromTWKB(\"" << geometryColumn_ << "\")) AS srid FROM ";
}
else
{
s << "SELECT ST_SRID(\"" << geometryColumn_ << "\") AS srid FROM ";
}
if (!geometry_table_.empty())
{
if (!schema_.empty())
@ -640,7 +647,14 @@ std::string postgis_datasource::populate_tokens(
}
else
{
s << " WHERE \"" << geometryColumn_ << "\" && " << box;
if (twkb_direct_)
{
s << " WHERE ST_GeomFromTWKB(\"" << geometryColumn_ << "\") && " << box;
}
else
{
s << " WHERE \"" << geometryColumn_ << "\" && " << box;
}
}
populated_sql += s.str();
}
@ -815,38 +829,47 @@ featureset_ptr postgis_datasource::features_with_context(query const& q,processo
if (twkb_encoding_)
{
// This will only work against PostGIS 2.2, or a back-patched version
// that has (a) a ST_Simplify with a "preserve collapsed" flag and
// (b) a ST_RemoveRepeatedPoints with a tolerance parameter and
// (c) a ST_AsTWKB implementation
// What number of decimals of rounding does the pixel size imply?
const int twkb_rounding = -1 * std::lround(log10(px_sz) + twkb_rounding_adjustment_) + 1;
// And what's that in map units?
const double twkb_tolerance = pow(10.0, -1.0 * twkb_rounding);
s << "SELECT ST_AsTWKB(";
s << "ST_Simplify(";
s << "ST_RemoveRepeatedPoints(";
if (simplify_clip_resolution_ > 0.0 && simplify_clip_resolution_ > px_sz)
if (twkb_direct_)
{
s << "ST_ClipByBox2D(";
s << "SELECT ";
s << "\"" << geometryColumn_ << "\"";
s << "AS geom";
}
s << "\"" << geometryColumn_ << "\"";
// ! ST_ClipByBox2D()
if (simplify_clip_resolution_ > 0.0 && simplify_clip_resolution_ > px_sz)
else
{
s << "," << sql_bbox(box) << ")";
}
// This will only work against PostGIS 2.2, or a back-patched version
// that has (a) a ST_Simplify with a "preserve collapsed" flag and
// (b) a ST_RemoveRepeatedPoints with a tolerance parameter and
// (c) a ST_AsTWKB implementation
// ! ST_RemoveRepeatedPoints()
s << "," << twkb_tolerance << ")";
// ! ST_Simplify(), with parameter to keep collapsed geometries
s << "," << twkb_tolerance << ",true)";
// ! ST_TWKB()
s << "," << twkb_rounding << ") AS geom";
// What number of decimals of rounding does the pixel size imply?
const int twkb_rounding = -1 * std::lround(log10(px_sz) + twkb_rounding_adjustment_) + 1;
// And what's that in map units?
const double twkb_tolerance = pow(10.0, -1.0 * twkb_rounding);
s << "SELECT ST_AsTWKB(";
s << "ST_Simplify(";
s << "ST_RemoveRepeatedPoints(";
if (simplify_clip_resolution_ > 0.0 && simplify_clip_resolution_ > px_sz)
{
s << "ST_ClipByBox2D(";
}
s << "\"" << geometryColumn_ << "\"";
// ! ST_ClipByBox2D()
if (simplify_clip_resolution_ > 0.0 && simplify_clip_resolution_ > px_sz)
{
s << "," << sql_bbox(box) << ")";
}
// ! ST_RemoveRepeatedPoints()
s << "," << twkb_tolerance << ")";
// ! ST_Simplify(), with parameter to keep collapsed geometries
s << "," << twkb_tolerance << ",true)";
// ! ST_TWKB()
s << "," << twkb_rounding << ") AS geom";
}
}
else
{
@ -1081,8 +1104,15 @@ box2d<double> postgis_datasource::envelope() const
}
else
{
s << "SELECT ST_XMin(ext),ST_YMin(ext),ST_XMax(ext),ST_YMax(ext)"
<< " FROM (SELECT ST_Extent(" <<geometryColumn_<< ") as ext from ";
s << "SELECT ST_XMin(ext),ST_YMin(ext),ST_XMax(ext),ST_YMax(ext)";
if (twkb_direct_)
{
s << " FROM (SELECT ST_Extent(ST_GeomFromTWKB(" << geometryColumn_<< ")) as ext from ";
}
else
{
s << " FROM (SELECT ST_Extent(" << geometryColumn_<< ") as ext from ";
}
if (extent_from_subquery_)
{

1
plugins/input/postgis/postgis_datasource.hpp
View file

@ -120,6 +120,7 @@ private:
int max_async_connections_;
bool asynchronous_request_;
bool twkb_encoding_;
bool twkb_direct_;
mapnik::value_double twkb_rounding_adjustment_;
mapnik::value_double simplify_snap_ratio_;
mapnik::value_double simplify_dp_ratio_;