Oracle7 Spatial Data Option User's Guide and Reference | ![]() Library |
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This chapter contains descriptions of the tuning functions and procedures shown in Table 6-1:
Table 6-1 Tuning Functions:
This function estimates the appropriate tiling level to use when indexing.
SDO_TUNE.ESTIMATE_TILING_LEVEL (layername, maxtiles, type_of_estimate)
The procedure returns an integer representing the level to use when creating a spatial index for the specified layer.
The SDO_ADMIN.POPULATE_INDEX and SDO_ADMIN.UPDATE_INDEX procedures are used to create or update the spatial index using fixed or variable-sized tiles. Store the value returned by the estimate_tiling_level() function in the sdo_level column of the <layername>_SDOLAYER table prior to building the spatial index.
For many applications, it is effective to call the estimate_tiling_level() function using the ALL_GID_EXTENT estimate type and a maximum of 10,000 tiles, as shown in Example 6-1.
set serveroutput on declare lev integer; begin lev:= mdsys.sdo_tune.estimate_tiling_level('SF_BLOCK_GPS',10000,
'ALL_GID_EXTENT'); dbms_output.put_line('VALUE is' ,|| lev); end;
The code shown in Example 6-2 generates a recommendation based on the extent of the defined coordinate system (latitude and longitude). This example returns a level whose tiles are not smaller than one degree cells.
set serveroutput on declare lev integer; begin lev := mdsys.sdo_tune.estimate_tiling_level('WORLD_CITIES', 360*180,
'LAYER_EXTENT'); dbms_output.put_line('VALUE is '|| lev); end;
This procedure determines the extent of all geometries in a layer.
SDO_TUNE.EXTENT_OF (layername, min_X, max_X, min_Y, max_Y))
This procedure returns the coordinates of the minimum bounding rectangle for all geometric data in a layer. Data type is number for the four return values.
None
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