A short overview of spatial support in MySQL 8.0, covering spatial data types, coordinate reference systems, functions and indexes, including examples

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MySQL 8.0 GIS Overview
Norvald H. Ryeng
Sofware Engineer
March 2018

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Agenda
Data Types
Spatal Reference Systems
Functons
Indexes
Upgrade Issues
1
2
3
4
5
6
7

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Data Types
● Geometry
– Point
– Linestring
– Polygon
– Geometry collecton
● Multpoint
● Multlinestring
● Multpolygon
Non-instantable, but can be used as column type.

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Spatal Reference Systems
SRID 0 Projected SRS
Cartesian SRS
5.7 8.0
Geographic SRS

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Spatal Reference Systems
● Each SRS has a unique spatal reference system ID (SRID)
– Numeric identfer
– 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 diferent SRIDs in one computaton
doesn't make sense and will raise an error (also in 5.7)

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Spatal Reference Systems
● 5107 predefned SRSs from the EPSG Dataset 9.2 (MySQL
8.0.4)
– 4628 projected
– 479 geographic
● Exposed through an INFORMATION_SCHEMA view,
ST_SPATIAL_REFERENCE_SYSTEMS
● CREATE/DROP SPATIAL REFERENCE SYSTEM statements to
create your own

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Example
CREATE TABLE cites (
id INTEGER AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(20) NOT NULL,
loc POINT SRID 4326 NOT NULL
);
INSERT INTO cites (name, loc) VALUES (
'Trondheim',
ST_GeomFromText('POINT(63.43048320193547 10.394972698312927)', 4326)
);
INSERT INTO cites (name, loc) VALUES (
'San Francisco',
ST_GeomFromText('POINT(37.2726156666666667 -122.44254551944445)', 4326)
);

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Functons
● 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

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Functons
● 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_Bufer, ST_Centroid, ST_ConvexHull, ST_Envelope,
ST_MakeEnvelope, ST_Simplify, ST_Diference, ST_Intersecton,
ST_SymDiference, ST_Union

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Functons

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Functons
● Measures
– ST_Area, ST_Distance, ST_Distance_Sphere, ST_Length
● Extract propertes
– 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 functons
– ST_LatFromGeohash, ST_LongFromGeohash, ST_Validate, ST_SwapXY

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Example
SELECT ST_Distance(
(SELECT loc FROM cites WHERE name='Trondheim'),
(SELECT loc FROM cites WHERE name='San Francisco')
) AS exact_distance;
exact_distance
8089891.633435546
SELECT ST_Distance_Sphere(
(SELECT loc FROM cites WHERE name='Trondheim'),
(SELECT loc FROM cites WHERE name='San Francisco')
) AS approx_distance;
approx_distance
8068723.414049273

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Indexes
● R-tree indexes on spatal data
– Cartesian or geographic, depending on SRID
● Geographic R-trees in InnoDB only
● Used automatcally by the optmizer
– Triggered by use of spatal relatons (ST_Within, etc.)
– Cost based decision making

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Example
CREATE SPATIAL INDEX loc_idx ON cites (loc);
SET @europe=ST_GeomFromText('POLYGON((2.49 83.51,-15.09 68.37,-28.80 66.19,-12.63 35.10,6.71
38.48,23.23 33.94,29.56 43.51,38.00 43.51,60.85 69.98,78.42 83.51,2.49 83.51))', 4326, 'axis-
order=long-lat');
SELECT name FROM cites WHERE ST_Within(loc, @europe);
exact_distance
Trondheim
EXPLAIN SELECT name FROM cites WHERE ST_Within(loc, @europe);
+----+-------------+--------+------------+-------+---------------+---------+---------+------+------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+--------+------------+-------+---------------+---------+---------+------+------+----------+-------------+
| 1 | SIMPLE | cities | NULL | range | loc_idx | loc_idx | 34 | NULL | 2 | 100.00 | Using where |
+----+-------------+--------+------------+-------+---------------+---------+---------+------+------+----------+-------------+

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Upgrade Issues

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Upgrade Issues
● YES, there are upgrade issues!
– We're sorry, but we have to …
● All EPSG SRSs are lattude frst, longitude second
– WKT and WKB input/output uses SRS axis order by default
● Can be overridden with 'axis-order=long-lat'
● Override opton not available in 5.7
– Earlier MySQL versions don't understand axis order, X=X and Y=Y
– Queries and/or scripts must be changed
● Storage format is stll longitude frst, lattude second
– Compatble with the limited geography support in 5.7

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Upgrade Issues
● SRID 0 is the safe choice if using MySQL pre 8.0
– Set correct SRS afer upgrading
● Indexes must be recreated afer upgrade
– Column defniton must be modifed to use SRID restricton frst
● The SRID restricton is not available in 5.7
– Indexes on columns without SRID restricton will never be used
● Ignored by the optmizer
● Allowed to exist in order to preserve dump-restore compatbility
● Warnings will be issued

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✓✓
Prepare Now
● Think through your use of SRIDs
– Use SRID 0 if you're unsure
● Use longitude-lattude ordering in 5.7
– But remember that import and export functons follow SRS defned
axis order in 8.0
● Use one SRID in each column
– Be ready to add SRID restrictons to columns and rebuild indexes in 8.0

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Feature descriptons and design details
directly from the source.
https:/ppmysslsserverteamy.comyp

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