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    Book: "Applying And Extending Oracle Spatial"
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    Optimized Rectangle to 5 Point Polygon
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    Simple Oracle C Sprintf or Java String.format
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    PLS-00306: wrong number or types of arguments in call to 'SDO_GEOMETRY'
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    ST_VertexN / ST_PointN - Extracting a specific point from any geometry
    Convert Single Point stored in SDO_ORDINATES to SDO_POINT_TYPE
    Aggregate APPEND Islands and XOR polygons
    Circular Arcs in Geodetic Polygons
    Some SDO_GEOMETRY/DIMINFO handling functions
    Changing all DIMINFO sdo_tolerance values for all metadata records in one go.
    Building Polygons from Incomplete Linestrings using ST_PolygonBuilder
    Computing Cardinal Directions to nearby geometries
    Intersecting two aggregated polygon layers with SC4O
    Spatial and Oracle 12c
    Update Triggers and SDO_GEOMETRY Equality
    Duplicate Geometry data and Data Models
    CENTROID package update
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    Compute Location from known Lat/Long point using delta easting and northing in miles
    Sorting SDO_GEOMETRY data using the ORDER BY clause of a SELECT statement
    Creating linestrings from points
    Rounding Coordinates or Ordinates in SDO_GEOMETRY
    Effects of Sdo_Geometry Ordinate Precision on Performance
    Effects of Sdo_Geometry Ordinate Precision on Storage
    The Spatial filtering of geometries: The effect of tolerances on relationships
    Application of Delaunay Triangulation and Inverse Distance Weighting (IDW) in Oracle for Soils Interpolation
    Selecting all SDO_GTYPE values for all tables/sdo_geometry columns in a schema
    CENTROID package - Tips for Use
    Announcing the Spatial Companion For Oracle (SC4O)
    Filtering Rings (Oracle Spatial)
    Splitting a polygon using one or more linestrings
    isValid, isSimple, Dimension and CoordDim methods for SDO_Geometry
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    ST_DeleteVertex for Oracle SDO_Geometry based on Jaspa/JTS
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    Constraining geometry type for sdo_geometry column in a table.
    CASE Statements and SDO_GEOMETRY
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    Oracle Spatial Forum - Melbourne April 2007
    Layer_GTypes for spatial indexes
    Oracle's SQL/MM Compliant Types
    Tips and Tricks



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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.

Filtering very short linestrings via bitmap function index

Thursday January 05 2012 at 02:16

Keywordsbitmap index function sdo_length short lines filtering large table

This article presents a method, using a function based bitmap index, for identifying and fast filtering short lines.

A colleague wrote to me today asking:

I’m looking for a way to improve a query to detect all line geometries which are shorter then 10 mm.

It takes days to check all our lines (full tabel scans on millions of rows);

Can’t I use the domain index to filter out the desired lines?

  1. DROP   TABLE Test10MM  PURGE;
  2. -- table TEST10MM dropped.
  3. CREATE TABLE Test10MM ( id INTEGER, geom mdsys.sdo_geometry );
  4. -- table TEST10MM created.
  5. INSERT INTO Test10MM (id, geom)
  6.      SELECT rownum,
  7.             mdsys.sdo_geometry(2002,NULL,NULL,
  8.                                 MDSYS.SDO_ELEM_INFO_ARRAY(1,2,1),
  9.                                 MDSYS.SDO_ORDINATE_ARRAY(
  10.                                    ROUND(dbms_random.VALUE(0,0.1),3),
  11.                                    ROUND(dbms_random.VALUE(0,0.1),3),
  12.                                    ROUND(dbms_random.VALUE(0,0.1),3),
  13.                                    ROUND(dbms_random.VALUE(0,0.1),3)))
  14.       FROM DUAL
  15.    CONNECT BY LEVEL <= 5000;
  16. -- 5,000 rows inserted.
  17. COMMIT;
  18. -- commited.
  19. SELECT 'Inserted '||COUNT(*)||' records into Test10MM' AS RecCount FROM Test10MM;
  20. -- RECCOUNT                                                                
  21. -- -----------------------------------------------------------------------
  22. -- Inserted 5000 records into Test10MM                                    
  24. -- 1 rows deleted.
  26.   v_shape mdsys.sdo_geometry;
  27. BEGIN
  28.   SELECT SDO_AGGR_MBR(geom) INTO v_shape FROM Test10MM;
  33. END;
  34. /
  36. -- anonymous block completed
  37. -- No Errors.
  38. COMMIT;
  39. -- commited.
  40. CREATE INDEX Test10MM_GEOM ON Test10MM(geom)
  41.        INDEXTYPE IS mdsys.spatial_index
  42.        parameters('sdo_indx_dims=2, layer_gtype=line');
  43. -- index TEST10MM_GEOM created.
  44. EXEC dbms_stats.gather_table_stats(ownname => 'CODESYS', tabname => 'TEST10MM', estimate_percent => 100, method_opt => 'for all indexed columns size auto' )
  45. -- anonymous block completed
  46. -- Normal filtering without index
  47. --
  48. SET autotrace ON EXPLAIN
  49. -- Autotrace Enabled
  50. -- Displays the execution plan only.
  51. SELECT COUNT(*) AS LenTo10mmCount
  52.   FROM Test10MM a
  53.  WHERE round(sdo_geom.sdo_length(a.geom,0.0005),2) <= 0.01;
  54. /*
  56. --------------
  57. 308
  58. Plan hash value: 2043904050
  59. -------------------------------------------------------------------------------
  60. | Id  | Operation          | Name     | Rows  | Bytes | Cost (%CPU)| Time     |
  61. -------------------------------------------------------------------------------
  62. |   0 | SELECT STATEMENT   |          |     1 |     8 |    26   (4)| 00:00:01 |
  63. |   1 |  SORT AGGREGATE    |          |     1 |     8 |            |          |
  64. |*  2 |   TABLE ACCESS FULL| TEST10MM |   250 |  2000 |    26   (4)| 00:00:01 |
  65. -------------------------------------------------------------------------------
  66. Predicate Information (identified by operation id):
  67. ---------------------------------------------------
  68.   2 - filter(ROUND("SDO_GEOM"."SDO_LENGTH"("A"."GEOM",0.0005),2)<=0.01)
  69. */
  70. -- Another method of identifying lines with length < 10mm
  71. --
  72. SELECT COUNT(*) AS tenmmcount
  73.   FROM Test10MM a
  74.  WHERE CASE WHEN round(sdo_geom.sdo_length(a.geom,0.0005),2) * 100 <= 1 THEN 1 ELSE 0 END = 1;
  75. /*
  76. TENMMCOUNT            
  77. ----------------------
  78. 308                    
  79. Plan hash value: 2043904050
  80. -------------------------------------------------------------------------------
  81. | Id  | Operation          | Name     | Rows  | Bytes | Cost (%CPU)| Time     |
  82. -------------------------------------------------------------------------------
  83. |   0 | SELECT STATEMENT   |          |     1 |     8 |    26   (4)| 00:00:01 |
  84. |   1 |  SORT AGGREGATE    |          |     1 |     8 |            |          |
  85. |*  2 |   TABLE ACCESS FULL| TEST10MM |   250 |  2000 |    26   (4)| 00:00:01 |
  86. -------------------------------------------------------------------------------
  87. Predicate Information (identified by operation id):
  88. ---------------------------------------------------
  89.    2 - filter(ROUND("SDO_GEOM"."SDO_LENGTH"("A"."GEOM",0.0005),2)*100<=1)
  90. */
  91. -- Can we create a function based index on this predicate?
  92. --
  93. CREATE bitmap INDEX Test10MM_10mm_idx ON Test10MM(CASE WHEN round(sdo_geom.sdo_length(geom,0.0005),2) * 100 <= 1 THEN 1 ELSE 0 END);
  94. /*
  95. SQL Error: ORA-30553: The function is not deterministic
  96. 30553. 00000 -  "The function is not deterministic"
  97. *Cause:    The function on which the index is defined is not deterministic
  98. *Action:   If the function is deterministic, mark it DETERMINISTIC.  If it
  99.            is not deterministic (it depends on package state, database state,
  100.            current time, or anything other than the function inputs) then
  101.            do not create the index.  The values returned by a deterministic
  102.            function should not change even when the function is rewritten or
  103.            recompiled.
  104. */
  105. -- No We can't
  106. -- Even if we could the use of functional index requires one to use the exact predicate in the query where clause!!!
  107. -- Let's wrap the predicate in a deterministic function
  108. --
  109. CREATE OR REPLACE FUNCTION is10mm(p_geom IN mdsys.sdo_geometry)
  110. RETURN NUMBER deterministic
  111. IS
  112. BEGIN
  113.   RETURN CASE WHEN round(sdo_geom.sdo_length(p_geom,0.0005),2) * 100 <= 1 THEN 1 ELSE 0 END;
  114. END is10mm;
  115. /
  116. SHOW errors
  117. -- FUNCTION is10mm compiled
  118. -- No Errors.
  119. -- Now create a bitmap index on the function
  120. --
  121. CREATE bitmap INDEX Test10MM_10mm_idx ON Test10MM(is10mm(geom));
  122. -- bitmap index TEST10MM_10MM_IDX created.
  123. -- Gather stats on it.
  124. --
  125. EXEC dbms_stats.gather_index_stats(ownname => 'CODESYS', indname => 'TEST10MM_10MM_IDX', estimate_percent => 100);
  126. -- anonymous block completed
  127. SET autotrace ON EXPLAIN
  128. -- Autotrace Enabled
  129. -- Displays the execution plan only.
  130. SELECT COUNT(*)
  131.   FROM Test10MM a
  132.  WHERE is10MM(geom) = 1;
  133. SET autotrace ON EXPLAIN
  134. -- Autotrace Enabled
  135. -- Displays the execution plan only.
  136. SELECT COUNT(*)
  137.   FROM Test10MM a
  138.  WHERE is10MM(geom) = 1;
  139. /*
  140. COUNT(*)              
  141. ----------------------
  142. 308                    
  143. Plan hash value: 577608402
  144. ---------------------------------------------------------------------------------------------------
  145. | Id  | Operation                     | Name              | Rows  | Bytes | Cost (%CPU)| Time     |
  146. ---------------------------------------------------------------------------------------------------
  147. |   0 | SELECT STATEMENT              |                   |     1 |     8 |     1   (0)| 00:00:01 |
  148. |   1 |  SORT AGGREGATE               |                   |     1 |     8 |            |          |
  149. |   2 |   BITMAP CONVERSION COUNT     |                   |    50 |   400 |     1   (0)| 00:00:01 |
  150. |*  3 |    BITMAP INDEX FAST FULL SCAN| TEST10MM_10MM_IDX |       |       |            |          |
  151. ---------------------------------------------------------------------------------------------------
  152. Predicate Information (identified by operation id):
  153. ---------------------------------------------------
  154.    3 - filter("CODESYS"."IS10MM"("GEOM")=1)
  155. */

Note that the query now correctly uses the bitmap index to speed the query achieving that which we set out to do.

The result is that a suitable function can be created that identifies small lines that can be used to execute fast queries against large tables. Of course, the result of the function is10MM could be cached or persisted in its own column and kept up to date via a trigger, but that is about implementation not the validity of the method.

I hope this is of use to someone.

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