PostGIS (PostgesSQL)Guía introductoria

Miguel Ángel Manso

ETSI en Topografía, Geodesia y Cartografía - UPM

Índice

• ¿Cómo crear una base de datos con la extensión espacial?

• ¿Cómo crear una tabla con Geometrías?

• ¿Cómo dar de alta los metadatos de la tabla?

• ¿Cómo crear un índice espacial?

• ¿Qué operaciones se pueden realizar con las geometrías?

Crear una base de datos con extensión espacial

• Si la base de datos es nueva:

– Lo ideal es realizarlo con el asistente de instalación de la base de datos

– Crea o añade, esta funcionalidad a una base de datos

• Si en la base de datos ya existe el template

– Crear la nueva base de datos indicando el template

¿Cómo saber si la base de datos es PostGIS?

• En el esquema public se habrán generado dos tablas:

• En el mismo esquema se dispondrá de un buen número de funciones

Crear una tabla con geometrías

• Usa la misma Clausura que para el resto de tablas: CREATE TABLE …();

• La columna que contendrá la geometría será de tipo: GEOMETRY

• Ejemplo:CREATE TABLE cola_markets (

mkt_id double precision NOT NULL,

name character varying( 32),

shape geometry);

Crear metadatos geometrías

• Existe la tabla geometry_columns en la que se registran las tablas que contienen alguna columna de tipo geometry

• Esta tabla contiene las siguientes columnas:

– F_TABLE_CATALOG, F_TABLE_SCHEMA, F_TABLE_NAME, F_GOMETRY_COLUM, COORD_DIMENSION, SRID, TYPE

Crear metadatos

INSERT INTO geometry_columns VALUES (

‘any’,

‘public ..’,

'cola_markets',

'shape',

2,

4326,

‘MULTIPOLYGON’);

AddGeometryColumn

• Existe la función AddGeometryColumn que realiza simultáneamente el alta del atributo en la tabla y crea los metadatosAddGeometryColumn(<schema_name>,<table_name>,<column_name>,<srid>,<type>,<dimension>)

• SELECT AddGeometryColumn(’public’, ’roads_geom’, ’geom’, 423, ’LINESTRING’, 2)

Crear índices espaciales

• Para crear índices SQL proporciona la siguiente clausura:

– CREATE INDEX nombre ON la_tabla USINGgist(la_columna);

• Ejemplo:

CREATE INDEX constru_the_geom_gist

ON public.constru

USING gist (the_geom);

Operaciones con las geometrías

• PostGIS clasifica las operaciones en los siguientes paquetes:– Management Functions– Geometry Constructors– Geometry Accessors– Geometry Editors– Geometry Outputs– Operators– Spatial Relationships and Measurements– Geometry Processing Functions– Linear Referencing– Long Transactions Support– Miscellaneous Functions– Exceptional Functions

Management FunctionsAddGeometryColumn - Adds a geometry column to an existing table of attributes.

DropGeometryColumn - Removes a geometry column from a spatial table.

DropGeometryTable - Drops a table and all its references in geometry_columns.

PostGIS_Full_Version - Reports full postgis version and build configuration infos.

PostGIS_GEOS_Version - Returns the version number of the GEOS library.

PostGIS_LibXML_Version - Returns the version number of the libxml2 library.

PostGIS_Lib_Build_Date - Returns build date of the PostGIS library.

PostGIS_Lib_Version - Returns the version number of the PostGIS library.

PostGIS_PROJ_Version - Returns the version number of the PROJ4 library.

PostGIS_Scripts_Build_Date - Returns build date of the PostGIS scripts.

PostGIS_Scripts_Installed - Returns version of the postgis scripts installed in this database.

PostGIS_Scripts_Released – Version number of the postgis.sql script released with the installed postgis lib.

PostGIS_Uses_Stats - Returns TRUE if STATS usage has been enabled.

PostGIS_Version - Returns PostGIS version number and compile-time options.

Populate_Geometry_Columns - Ensures geometry columns have appropriate spatial constraints and exist in the geometry_columns table.

Probe_Geometry_Columns - Scans all tables with PostGIS geometry constraints and adds them to the geometry_columns table if they are not there.

UpdateGeometrySRID - Updates the SRID of all features in a geometry column, and in geometry_columns

Geometry Constructors

ST_MakeBox2D

ST_MakeBox3D

ST_MakeLine

ST_MakeEnvelope

ST_MakePolygon

ST_MakePoint

ST_MakePointM

ST_MLineFromText

ST_MPointFromText

ST_MPolyFromText

ST_Point

ST_PointFromText ST_PointFromWKB

ST_Polygon -

ST_PolygonFromText

ST_WKBToSQL

ST_WKTToSQL

ST_BdPolyFromText

ST_BdMPolyFromText

ST_GeogFromText

ST_GeographyFromText

ST_GeogFromWKB

ST_GeomCollFromText

ST_GeomFromEWKB

ST_GeomFromEWKT

ST_GeometryFromText

ST_GeomFromGML

ST_GeomFromKML

ST_GMLToSQL

ST_GeomFromText

ST_GeomFromWKB.

ST_LineFromMultiPoint

ST_LineFromText

ST_LineFromWKB

ST_LinestringFromWKB

Geometry AccessorsGeometryType

ST_Boundary

ST_CoordDim

ST_Dimension

ST_EndPoint

ST_Envelope

ST_ExteriorRing -

ST_GeometryN

ST_GeometryType

ST_InteriorRingN

ST_IsClosed

ST_IsEmpty

ST_IsRing

ST_IsSimple

ST_IsValid

ST_IsValidReason

ST_M

ST_NDims

ST_NPoints

ST_NRings

ST_NumGeometries -

ST_NumInteriorRings

ST_NumInteriorRing

ST_NumPoints

ST_PointN

ST_SRID -

ST_StartPoint

ST_Summary -

ST_X

ST_Y

ST_Z -

ST_Zmflag

Geometry EditorsST_AddPoint

ST_Affine

ST_Force_2D

ST_Force_3D

ST_Force_3DZ

ST_Force_3DM

ST_Force_4D

ST_Force_Collection

ST_ForceRHR

ST_LineMerge

ST_CollectionExtract

ST_Multi

ST_RemovePoint

ST_Reverse

ST_RotateST_RotateXST_RotateYST_RotateZST_ScaleST_SegmentizeST_SetPointST_SetSRIDST_SnapToGridST_TransformST_TranslateST_TransScale

Geometry Outputs

ST_AsBinary – Return WKB representation of the geometry without SRID metadata.

ST_AsEWKB – Return WKB representation of the geometry with SRID metadata.

ST_AsEWKT – Return WKT representation of the geometry with SRID metadata.

ST_AsGeoJSON - Return the geometry as a GeoJSON element.

ST_AsGML - Return the geometry as a GML version 2 or 3 element.

ST_AsHEXEWKB - Returns a Geometry in HEXEWKB format (as text) using either little-endian (NDR) or

big-endian (XDR) encoding.

ST_AsKML - Return the geometry as a KML element. Several variants.

ST_AsSVG - Returns a Geometry in SVG path data given a geometry object.

ST_GeoHash - Return a GeoHash representation (geohash.org) of the geometry.

ST_AsText – Return WKT representation of the geometry without SRID metadata.

Operators

&& - Returns TRUE if A's bounding box overlaps B's.&< - Returns TRUE if A's bounding box overlaps or is to the left of B's.&<| - Returns TRUE if A's bounding box overlaps or is below B's.&> - Returns TRUE if A' bounding box overlaps or is to the right of B's.<< - Returns TRUE if A's bounding box is strictly to the left of B's.<<| - Returns TRUE if A's bounding box is strictly below B's.= - Returns TRUE if A's bounding box is the same as B's.>> - Returns TRUE if A's bounding box is strictly to the right of B's.@ - Returns TRUE if A's bounding box is contained by B's.|&> - Returns TRUE if A's bounding box overlaps or is above B's.|>> - Returns TRUE if A's bounding box is strictly above B's.~ - Returns TRUE if A's bounding box contains B's.~= - Returns TRUE if A's bounding box is the same as B's.

Relationships and MeasurementsST_Area

ST_Azimuth

ST_Centroid

ST_ClosestPoint

ST_Contains

ST_ContainsProperly

ST_Covers

ST_CoveredBy

ST_Crosses

ST_LineCrossingDirection

ST_Disjoint

ST_Distance

ST_HausdorffDistance

ST_MaxDistance

ST_Distance_Sphere

ST_Distance_Spheroid

ST_DFullyWithin

ST_Dwithin

ST_Equals

ST_HasArc

ST_Intersects

ST_Length

ST_Length2D

ST_Length3D

ST_Length_Spheroid

ST_Length2D_Spheroid

ST_Length3D_Spheroid

ST_LongestLine

ST_OrderingEquals

ST_Overlaps

ST_Perimeter

ST_Perimeter2D

ST_Perimeter3D

ST_PointOnSurface

ST_Relate

ST_ShortestLine

ST_Touches

ST_Within

Geometry Processing Functions

ST_BufferST_BuildAreaST_CollectST_ConvexHullST_CurveToLineST_DifferenceST_DumpST_DumpPointsST_DumpRingsST_IntersectionST_LineToCurveST_MemUnionST_MinimumBoundingCircleST_PolygonizeST_Shift_LongitudeST_SimplifyST_SimplifyPreserveTopologyST_SymDifferenceST_Union

Linear Referencing

ST_Line_Interpolate_Point - Returns a point interpolated along a line. Second argument is a float8 between 0 and 1 representing of total length of linestring the point has to be located.

ST_Line_Locate_Point - Returns a float between 0 and 1 representing the location of the closest point on LineString to the given Point, as a fraction of total 2d line length.

ST_Line_Substring - Return a linestring being a substring of the input one starting and ending at the given fractions of total 2d length. Second and third arguments are float8 values between 0 and 1.

ST_Locate_Along_Measure - Return a derived geometry collection value with elements that match the specified measure. Polygonal elements are not supported.

ST_Locate_Between_Measures - Return a derived geometry collection value with elements that match the specified range of measures inclusively. Polygonal elements are not supported.

ST_LocateBetweenElevations - Return a derived geometry (collection) value with elements that intersect the specified range of elevations inclusively. Only 3D, 4D LINESTRINGS and MULTILINESTRINGS are supported.

ST_AddMeasure - Return a derived geometry with measure elements linearly interpolated between the start and end points. If the geometry has no measure dimension, one is added. If the geometry has a measure dimension, it is over-written with new values. Only LINESTRINGS and MULTILINESTRINGS are supported.

Long Transactions

AddAuth - Add an authorization token to be used in current transaction.

CheckAuth - Creates trigger on a table to prevent/allow updates and deletes of rows based on authorization token.

DisableLongTransactions - Disable long transaction support. This function removes the long transaction support metadata tables, and drops all triggers attached to lock-checked tables.

EnableLongTransactions - Enable long transaction support. This function creates the required metadata tables, needs to be called once before using the other functions in this section. Calling it twice is harmless.

LockRow - Set lock/authorization for specific row in tableUnlockRows - Remove all locks held by specified authorization id.

Returns the number of locks released.

Miscellaneous Functions

ST_Accum - Aggregate. Constructs an array of geometries.Box2D - Returns a BOX2D representing the maximum extents of the geometry.Box3D - Returns a BOX3D representing the maximum extents of the geometry.ST_Estimated_Extent - Return the 'estimated' extent of the given spatial table. The estimated is taken

from the geometry column's statistics. The current schema will be used if not specified.ST_Expand - Returns bounding box expanded in all directions from the bounding box of the input

geometry. Uses double-precisionST_Extent - an aggregate function that returns the bounding box that bounds rows of geometries.ST_Extent3D - an aggregate function that returns the box3D bounding box that bounds rows of

geometries.Find_SRID - Function returns the integer SRID of the specified column by searching through the

GEOMETRY_COLUMNS table.ST_Mem_Size - Returns the amount of space (in bytes) the geometry takes.ST_Point_Inside_Circle - Is the point geometry insert circle defined by center_x, center_y , radiusST_XMax - Returns X maxima of a bounding box 2d or 3d or a geometry.ST_XMin - Returns X minima of a bounding box 2d or 3d or a geometry.ST_YMax - Returns Y maxima of a bounding box 2d or 3d or a geometry.ST_YMin - Returns Y minima of a bounding box 2d or 3d or a geometry.ST_ZMax - Returns Z minima of a bounding box 2d or 3d or a geometry.ST_ZMin - Returns Z minima of a bounding box 2d or 3d or a geometry.

Exceptional Functions

PostGIS_AddBBox - Add bounding box to the geometry.

PostGIS_DropBBox - Drop the bounding box cache from the geometry.

PostGIS_HasBBox - Returns TRUE if the bbox of this geometry is cached, FALSE otherwise.