Spatial Data in MySQL 8 - Percona · MySQL 5.7 doesn't know about latitudes and longitudes – Everything is Cartesian X and Y – But a few functions expect X=longitude and Y=latitude

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Spatial Data in MySQL 8.0

Norvald H. RyengSoftware Engineer

3Copyright © 2017 Oracle and/or its affiliates. All rights reserved.

Safe Harbor Statement

The following is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. The development, release, and timing of any features or functionality described for Oracle's products remains at the sole discretion of Oracle.


AgendaGIS basics

Demo

Preparing for the upgrade to 8.0

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GIS Basics


“GIS is a form of digital mapping technology. Kind of like Google Earth, but better.”— Arnold Schwarzenegger, Governor of California


Data Types● Geometry

– Point

– Linestring

– Polygon

– Geometry collection● Multipoint

● Multilinestring

● Multipolygon

Non-instantiable, but can be used as column type.


Spatial Reference Systems

SRID 0 Projected SRS Geographic SRS

Cartesian SRS

5.7 8.0


Spatial Reference Systems● Each SRS has a unique spatial reference system ID (SRID)

– Numeric identifier

– No formal standard/catalog of SRIDs

– De facto standard: EPSG Dataset● 4326 = WGS 84 (“GPS coordinates”)

● 3857 = WGS 84 / World Mercator (“Web Mercator”)

● A property of each geometry value

● Mixing geometries in different SRIDs in one computation doesn't make sense and will raise an error (also in 5.7)


Data TypesCREATE TABLE t ( g GEOMETRY, pt POINT NOT NULL, ls LINESTRING SRID 0, py POLYGON SRID 4326 NOT NULL);

INSERT INTO t (pt, py) VALUES ( POINT(0, 0), ST_GeomFromText('POLYGON((0 0, 10 0, 10 10, 0 0))', 4326));


Import Functions● Linestring(Point(0, 0), Point(1, 0), Point(2, 2))

● ST_GeomFromText('POINT(0 0)', 4326)

● ST_PolyFromText('POLYGON((0 0, 10 0, 10 10, 0 0))', 4326, 'axis-order=long-lat')

● ST_PointFromGeohash('gc7x3q7t60', 4326)

● ST_GeomFromGeoJSON('{"type":"Point","coordinates":[102.0, 0.0]}')


Export Functions● ST_AsText(@geometry)

● ST_AsBinary(@geometry, 'axis-order=lat-long')

● ST_AsGeoJSON(@geometry)

● ST_Geohash(@point, 10)


Functions● Import

– ST_GeomCollFromTxt/ST_GeomCollFromText, ST_GeomCollFromWKB, ST_GeomFromGeoJSON, ST_GeomFromText, ST_GeomFromWKB, ST_LineFromText, ST_LineFromWKB, ST_MLineFromText, ST_MLineFromWKB, ST_MPointFromText, ST_MPointFromWKB, ST_MPolyFromText, ST_MPolyFromWKB, ST_PointFromGeohash, ST_PolyFromText, ST_PolyFromWKB

● Export

– ST_AsBinary, ST_AsGeoJSON, ST_AsText, ST_Geohash


Functions● Comparison

– ST_Contains, ST_Crosses, ST_Disjoint, ST_Equals, ST_Intersects, ST_Overlaps, ST_Touches, ST_Within

– MBRContains, MBRCoveredBy, MBRCovers, MBRDisjoint, MBREquals, MBRIntersects, MBROverlaps, MBRTouches, MBRWithin

● Produce new geometries

– ST_Buffer, ST_Centroid, ST_ConvexHull, ST_Envelope, ST_MakeEnvelope, ST_Simplify, ST_Difference, ST_Intersection, ST_SymDifference, ST_Union


Set Operations


Functions● Measures

– ST_Area, ST_Distance, ST_Distance_Sphere, ST_Length

● Extract properties

– ST_Dimension, ST_EndPoint, ST_ExteriorRing, ST_GeometryN, ST_GeometryType, ST_InteriorRingN, ST_IsClosed, ST_IsEmpty, ST_IsSimple, ST_IsValid, ST_PointN, ST_SRID, ST_StartPoint, ST_X, ST_Y

● Helper functions

– ST_LatFromGeohash, ST_LongFromGeohash, ST_Validate, ST_SwapXY


Spatial Indexes● Column must be NOT NULL to create index

● Column must have SRID restriction, or index is not used

– New requirement in 8.0

– Geographic indexes only available in InnoDB

● Used automatically by the optimizer based on cost model

● Triggered by the use of spatial relation functions

– ST_Within, MBRWithin, ST_Contains, etc.


“Geography is just physics slowed down, with a couple of trees stuck in it.”— Terry Pratchett in The Last Continent


Demo


LAMPFrontend

● OpenLayers 4.3.2

Backend

● Ubuntu 16.04 LTS

● Apache 2.4.18

● PHP 7.0 using mysqli

– Thin wrapper to run queries and return result to web app

● MySQL 8.0

– InnoDB with spatial index

– Produce GeoJSON output


What can I do now to prepare for what's coming?


Use the Right SRID● MySQL 5.7 and older assumed everything was Cartesian

– Ignored SRID

● If you know what you're doing, use the correct SRID

– Beware of geographic computations in 8.0

● If unsure, use SRID 0

– No surprises when upgrading to 8.0

– Makes no claim about the SRS except that it's flat


Axis Order● MySQL 5.7 doesn't know about latitudes and longitudes

– Everything is Cartesian X and Y

– But a few functions expect X=longitude and Y=latitude

● MySQL 8.0 expects import/export to be in the SRS axis order

– Manual override is possible

● MySQL 8.0 uses SRSs from the EPSG Dataset

– All EPSG defined SRSs use latitude-longitude axis ordering

– MySQL 8.0 stores data as X=longitude and Y=latitude


One SRID in Each Column● Mixed SRID indexes are not usable

– Will never be considered by the 8.0 optimizer

– You will be allowed to create it (to ensure dump-restore compatibility)

● Mixed SRID in non-indexed columns is OK

– May even be what you want

– Restricts the computations you can do (no mixing of SRIDs)


✓✓Prepare Now● Think through your use of SRIDs

– Use SRID 0 if you're unsure

● Use longitude-latitude ordering in 5.7

– But remember that import and export functions follow SRS defined axis order in 8.0

● Use one SRID in each column

– Be ready to rebuild indexes in 8.0


Feature descriptions and design detailsdirectly from the source.

http://mysqlserverteam.com/


Documents

Spatial Data in MySQL 8 - Percona · MySQL 5.7 doesn't know about latitudes and longitudes – Everything is Cartesian X and Y – But a few functions expect X=longitude and Y=latitude