SQLBits X Training Day Presentation on SQL Server 2012 Spatial Indexing Copyright (c) Microsoft Corp.

2. : How do I tell?
A: SELECT * FROM T WHERE g.STIntersects(@x) = 1

3. SELECT *
FROM T WITH(INDEX(T_g_idx))
WHERE g.STIntersects(@x) = 1

4. Plan choice is cost-based
QO uses various information, including cardinality
EXEC sp_executesql
SELECT
DECLARE*@x geometry = 'POINT (0 0)'
SELECT N'SELECT *
FROM T *
WHERE FROM T
FROM TT.g.STIntersects('POINT (0 0)') = 1
WHERE T.g.STIntersects(@x) = 1',
WHERE T.g.STIntersects(@x) = 1
N'@x geometry', N'POINT (0 0)'
When can we estimate cardinality?
Variables: never
Literals: not for spatial since they are not literals under the covers
Parameters: yes, but cached, so first call matters

5. C
B D A B A B
D A
Primary Filter Secondary Filter
E (Index lookup) (Original predicate)
In general, split predicates in two
Primary filter finds all candidates, possibly
with false positives (but never false negatives)
Secondary filter removes false positives
The index provides our primary filter
Original predicate is our secondary filter
Some tweaks to this scheme
Sometimes possible to skip secondary filter

8. Secondary Filter
IndexingFilter
Primary Phase
1 2 15 16
1.
4 3 14 13
5 8 9 12
3.
6 7 10 11
2.
5.
4. Apply actual on the spatial
3. Intersecting grids method
2. Identify a gridfor query on
1. Overlay gridsCLR spatialobject(s)
identifies
candidates to find matches
object to store in index

10. /4/2/3/1
/
(“cell 0”)
Deepest-cell Optimization: Only keep the lowest level cell in index
Covering Optimization: Only record higher level cells when all lower
cells are completely covered by the object
Cell-per-object Optimization: User restricts max number of cells per object

11. 0 – cell at least touches the object (but not 1 or 2)
Spatial Reference ID
1 – guarantee thatto be encoding
Varbinary(5) the same to produce
Have object partially covers cell
15 columns and 2 – object covers cell id
895 byte limitation
of grid cell
match
Prim_key geography Prim_key cell_id srid cell_attr
1 0x00007 42 0
1 g1
3 0x00007 42 1
2 g2 3 0x0000A 42 2
3 g3 3 0x0000B 42 0
3 0x0000C 42 1
Base Table T 1 0x0000D 42 0
2 0x00014 42 1
CREATE SPATIAL INDEX sixd Internal Table for sixd
ON T(geography)

14. Create index example GEOMETRY:
CREATE SPATIAL INDEX sixd ON spatial_table(geom_column)
WITH (BOUNDING_BOX = (0, 0, 500, 500),
GRIDS = (LOW, LOW, MEDIUM, HIGH),
CELLS_PER_OBJECT = 20)
Create index example GEOGRAPHY:
CREATE SPATIAL INDEX sixd ON spatial_table(geogr_column)
USING GEOGRAPHY_GRID
WITH (GRIDS = (LOW, LOW, MEDIUM, HIGH),
CELLS_PER_OBJECT = 20)
NEW IN SQL Server 2012 (equivalent to default creation):
CREATE SPATIAL INDEX sixd ON spatial_table(geom_column)
USING GEOGRAPHY_AUTO_GRID
WITH (CELLS_PER_OBJECT = 20)
14 Use ALTER and DROP INDEX for maintenance.

16. Geometry:
STIntersects() = 1 •
•
STOverlaps() = 1
•
STEquals()= 1 •
STTouches() = 1 •
•
STWithin() = 1
•
STContains() = 1 •
STDistance() < val •
STDistance() <= val
Nearest Neighbor
Filter() = 1

19. Itself
Ancestors
Descendants
7 7.2 7.2.4
Spatial Index S

20. Optional Sort Remove dup ranges
T(@g)
Ranges
Spatial Index Seek

21. Fully contained
cells
Partially
contained cells

22. Optimal value (theoretical) is
somewhere between two extremes
Default values: Time needed to
512 - Geometry AUTO grid process false positives
768 - Geography AUTO grid
1024 - SELECT * FROM table t WITH
MANUAL grids (SPATIAL_WINDOW_MAX_CELLS=256)
WHERE t.geom.STIntersects(@window)=1;

28. Give me the closest 5 Italian restaurants
SQL Server 2008/2008 R2: table scan
SQL Server 2012: uses spatial index
SELECT TOP(5) *
FROM Restaurants r
WHERE r.type = ‘Italian’
AND r.pos.STDistance(@me) IS NOT NULL
ORDER BY r.pos.STDistance(@me)

30. Find the closest 50 business points to a specific location (out of 22 million in total)

37. sp_spatial_help_geometry_histogram
sp_spatial_help_geography_histogram
Used for spatial data and index analysis

39. Arguments
Parameter Type Description
@tabname nvarchar(776) the name of the table for which the index has been specified
@indexname sysname the index name to be investigated
@verboseoutput tinyint 0 core set of properties is reported
1 all properties are being reported
@query_sample geometry A representative query sample that will be used to test the
usefulness of the index. It may be a representative object or a
query window.
PropName: nvarchar(256) PropValue: sql_variant

40. Parameter Type Description
@tabname nvarchar(776) the name of the table for which the index has been
specified
@indexname sysname the index name to be investigated
@verboseoutput tinyint 0 core set of properties is reported
1 all properties are being reported
@query_sample geography A representative query sample that will be used to
test the usefulness of the index. It may be a
representative object or a query window.
@xml_output xml This is an output parameter that contains the
returned properties in an XML fragment

41. Property Type Description
Base_Table_Rows Bigint All Number of rows in the base table
Index properties - All index properties: bounding box, grid densities, cell per object
Total_Primary_Index_R Bigint All Number of rows in the index
ows
Total_Primary_Index_P Bigint All Number of pages in the index
ages
Total_Number_Of_Obje Bigint Core Indicates whether the representative query sample falls outside of the
ctCells_In_Level0_For_ bounding box of the geometry index and into the root cell (level 0 cell). This is
QuerySample either 0 (not in level 0 cell) or 1. If it is in the level 0 cell, then the
investigated index is not an appropriate index for the query sample.
Total_Number_Of_Obje Bigint Core Number of cell instances of indexed objects that are tessellated in level 0. For
ctCells_In_Level0_In_I geometry indexes, this will happen if the bounding box of the index is smaller
ndex than the data domain.
A high number of objects in level 0 may require a costly application of
secondary filters if the query window falls partially outside the bounding box.
If the query window falls inside the bounding box, having a high number of
objects in level 0 may actually improve the performance.

42. Property Type Description
Number_Of_Rows_Selected_By_Primary_ bigint Core P = Number of rows selected by the primary filter.
Filter
Number_Of_Rows_Selected_By_Internal_ bigint Core S = Number of rows selected by the internal filter. For
Filter these rows, the secondary filter is not called.
Number_Of_Times_Secondary_Filter_Is_ bigint Core Number of times the secondary filter is called.
Called
Percentage_Of_Rows_NotSelected_By_Pri float Core Suppose there are N rows in the base table, suppose P
mary_Filter are selected by the primary filter. This is (N-P)/N as
percentage.
Percentage_Of_Primary_Filter_Rows_Sele float Core This is S/P as a percentage. The higher the percentage,
cted_By_Internal_Filter the better is the index in avoiding the more expensive
secondary filter.
Number_Of_Rows_Output bigint Core O=Number of rows output by the query.
Internal_Filter_Efficiency float Core This is S/O as a percentage.
Primary_Filter_Efficiency float Core This is O/P as a percentage. The higher the efficiency is,
the less false positives have to be processed by the
secondary filter.

46. http://social.technet.microsoft.com/wiki/contents/articles/updated-spatial-features-in-the-sql-
azure-q4-2011-service-release.aspx
Forum: http://forums.microsoft.com/MSDN/ShowForum.aspx?ForumID=1629&SiteID=1