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Current SQL Server Blog Articles

    STGeometryTypes: Extracting all geometry type string values from complex geometry
    STDensify: Densify (m)LineString or (m)Polygon geometry objects
    STInsertN: Insert single vertex into a geometry
    STUpdateN: Update (replace) a single vertex within a geometry object.
    STUpdate: Replace all points equal to the supplied point with replacement point.
    STDeleteN: Delete single vertex from geometry
    STDelete: Deleting vertices in geometry objects
    STFlipVectors: Normalize direction of linestring vectors
    STConvertToLineString: Extract LineStrings in GeometryCollection to create LineString
    STLine2Cogo: Converting LineStrings to COGO XML
    STCogo2Line: Creating (Multi)LineStrings geometries from COGO XML instructions
    STVectorize: Break Linestring/Polygon elements into 2 point vectors (or 3 point circular curves)
    STScale: Function to Scale a geometry object
    TSQL String Tokenizer Function for SQL Server
    STGeometry2MBR/STGeography2MBR: Compute and return MBR ordinates
    generate_series for SQL Server 2008
    STExtractPolygon: Extract Polygons from result of STIntersection in SQL Server Spatial
    STRound: Function to round ordinates of a SQL Server Spatial geometry object
    STExtract: Extract elements of a geometry object
    STNumRings: Counting number of polygon rings
    STFilterRings: Removing rings from Polygon based on area.
    STMove: Function to Move a geometry object in SQL Server Spatial
    STCentroid*: Alternate Functions for Compute a Centroid
    STRotate: Function to rotate a geometry object in SQL Server Spatial
    STVertices: Wrapper over STDumpPoints
    STMorton: Creating a Morton number Space Key value for grid square
    Gridding a geometry or geography object (SQL Server Denali)
    On hinting spatial indexes
    RandomSearchByExtent: Random Search Procedure (2008 Spatial)
    COGO: Convert DMS String to decimal degrees floating point number.
    COGO: Converting (Google Earth) Formatted Longitude/Latitude points to decimal degrees (SQL Server)
    COGO: Convert Degrees, Minutes and Seconds values to Decimal Degrees
    COGO: DD2DMS Formatting a latitude/longitude decimal degree value
    COGO: Create point from bearing and distance
    COGO: Compute number of vertices required to stroke circle or circular arc
    COGO: Calculating the bearing between two points (SQL Server 2008 Spatial)
    COGO: Compute arc length subtended by angle centre of circle
    COGO: Compute chord length of segment of a circle (arc)
    COGO: Computing Arc To Chord (Arc2Chord) Separation
    COGO: Creating a stroked polygon from a circle's centre x,y and radius
    COGO: Finding centre and radius of a curve defined by three points: FindCircle function
    CheckRadii: Identifying Tight Radius Curves sections within LineString geometry data
    Generating random point data for SQL Server 2008 Spatial
    New Presentation on Active (Searchable) Spatial Metadata for SQL Server 2008 Spatial and FreeText
    STisGeo: Checking if a column in a table or a view is of type geometry or geography
    Vectorising geometry objects in SQL Server 2008
    STMBR2Geometry/STMBR2Geography functions
    Extracting geometry types from geometry/geography objects in SQL Server 2008
    Getting the number of coordinate dimensions of a geometry/geography object in SQL Server 2008
    STDumpPoints: A Function that Dumps the Vertices/Points in a geometry
    toGeography and toGeography Conversion Functions for SQL Server 2008 Spatial
    Write text file with spatial data from SQL Server 2008
    Loading Shapefiles into Geography type column in SQL Server 2008
    Tip #6: Correcting invalid geometries
    Tip #5: Where or where has my little column gone
    Tip #4: What Coordinate System is that?
    Tip #3: What object is that?
    Tip #2: Spatial Indexing and Primary Keys
    Tip #1: SQL Server 2008 "Katmai" - Setting SRIDs



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All Blog Articles, Data Models and Free Source Code by Simon Greener, The SpatialDB Advisor is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

On hinting spatial indexes

Wednesday September 28 2011 at 00:55

Recently, using SQL Server 2008 (not R2), I came across an issue with hinting a SELECT statement with a spatial index. This particular issue is different from the one Bob Beauchem wrote about in his article On hinting spatial indexes and query complexity (in turn he references Isaac Kunen’s Is my spatial index being used?).

The difference with the issue I found is to do with a very simple query that uses a constructed geometry. Here is the original coding of the query:

  2.   FROM dbo.admin_sorted a
  3.   WITH (INDEX (admin_sorted_geom))
  4.  WHERE a.geom.STIntersects(geometry::STLineFromText('LINESTRING(320000,5340000,321000,5341000)',a.geom.STSrid)) = 1;
  5. -- Result
  6. Msg 8635, Level 16, State 8, Line 1
  7. The query processor could NOT produce a query plan FOR a query WITH a spatial INDEX hint.  Reason: The spatial parameter REFERENCES a COLUMN that IS defined below the predicate.  Try removing the INDEX hints OR removing SET FORCEPLAN.

Now, there could not be anything more simple that this query, so why is an error being thrown?

Following a hunch I discovered (I think) that the geometry::STLineFromText() constructor is the culprit. On this basis, I played around with the query and, using a CTE, came up with the following that correctly uses the spatial index.

Note: The reason for the “(SELECT TOP 1…. )” in the CTE is because I want the constructed linestring to have the same SRID as the host table.

  1. WITH sg AS (
  2.   SELECT geometry::STLineFromText('LINESTRING(300000 5200000,500000 5400000)',a.Geom.STSrid) AS geom
  3.     FROM (SELECT TOP 1 geom
  4.             FROM  dbo.admin_sorted) a
  5. )
  6. SELECT COUNT(*) AS AdminCount
  7.   FROM sg a,
  8.        dbo.admin_sorted b
  9.   WITH (INDEX (admin_sorted_geom))
  10.  WHERE b.geom.STIntersects(a.geom) = 1;
  11. -- Results
  12. AdminCount
  13. ----------
  14. 101

Here is that part of the actual explanation plan showing the use of the spatial index.

Perhaps this is no longer an issue in R2 or Denali.

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