Oracle Spatial User's Guide and Reference Release 8.1.6 A7713201 

This chapter describes how to load spatial data into a database, including storing the data in a table with a column of type SDO_GEOMETRY and creating a spatial index for it.
The following steps will enable you to efficiently query spatial data:
The process of loading data can be classified into two categories:
This process is used to load large volumes of data into the database and uses the SQL*Loader utility to load the data.
This process is used to insert relatively small amounts of data into the database using the INSERT statement in SQL.
Bulk loading can import large amounts of ASCII data into an Oracle database. Bulk loading is accomplished with the SQL*Loader utility. (For information about SQL*Loader, see the Oracle8i Utilities manual.)
The following example assumes a table called POLY_4PT was created as follows:
CREATE TABLE POLY_4PT (GID VARCHAR2(32), GEOMETRY MDSYS.SDO_GEOMETRY);
Assume that the ASCII data consists of a file with delimited columns and separate rows fixed by the limits of the table with the following format:
geometry rows: GID, GEOMETRY
The coordinates in the geometry column represent roads for a region. Example 31 shows the control file for loading the roads and attributes.
LOAD DATA INFILE * TRUNCATE CONTINUEIF NEXT(1:1) = '#' INTO TABLE POLY_4PT FIELDS TERMINATED BY '' TRAILING NULLCOLS ( GID INTEGER EXTERNAL, GEOM COLUMN OBJECT ( SDO_GTYPE INTEGER EXTERNAL, SDO_ELEM_INFO VARRAY TERMINATED BY '/' (X FLOAT EXTERNAL), SDO_ORDINATES VARRAY TERMINATED BY '/' (Y FLOAT EXTERNAL) ) ) begindata 13131/ #+ #122.421537.7862122.42237.7869122.42137.789122.4237.7866 #122.421537.7862/ 23131/ #+ #122.401937.8052122.402737.8055122.403137.806122.401237.8052 #122.401937.8052/ 33131/ #122.42637.803122.424237.8053122.4235537.8044122.423537.8025 #122.42637.803/
Example 32 shows a control file for loading a table with point data.
LOAD DATA INFILE * TRUNCATE CONTINUEIF NEXT(1:1) = '#' INTO TABLE POINT FIELDS TERMINATED BY '' TRAILING NULLCOLS ( GID INTEGER EXTERNAL, GEOMETRY COLUMN OBJECT ( SDO_GTYPE INTEGER EXTERNAL, SDO_POINT COLUMN OBJECT (X FLOAT EXTERNAL, Y FLOAT EXTERNAL) ) ) BEGINDATA 1 1 122.4215 37.7862 2 1 122.4019 37.8052 3 1 122.426 37.803 4 1 122.4171 37.8034 5 1 122.416151 37.8027228
Oracle Spatial uses standard Oracle8i tables that can be accessed or loaded with standard SQL syntax. This section contains examples of transactional inserts into columns of type SDO_GEOMETRY. Note that SQL statements in Oracle8i have a limit of 999 arguments. Therefore, you cannot create a variablelength array of more than 999 elements using the SDO_GEOMETRY constructor inside a transactional INSERT statement; however, you can insert a geometry using a host variable, and the host variable can be built using the SDO_GEOMETRY constructor with more than 999 values in the SDO_ORDINATE_ARRAY specification. (The host variable is an OCI, PL/SQL, or Java program variable.).
The geometry to be stored is a polygon with a hole, as shown in Figure 31. The coordinate values for elements 1 and 2 are:
Element 1= [P1(6,15), P2(10,10), P3(20,10), P4(25,15), P5(25,35), P6(19,40),
P7(11,40), P8(6,25), P1(6,15)] Element 2= [H1(12,15), H2(15,24)]
This example assumes that table Parks was created as follows:
CREATE TABLE PARKS (NAME VARCHAR2(32), SHAPE MDSYS.SDO_GEOMETRY);
The SQL statement for inserting the data for geometry OBJ_1 is:
INSERT INTO PARKS VALUES ('OBJ_1', MDSYS.SDO_GEOMETRY(2003, NULL,NULL, MDSYS.SDO_ELEM_INFO_ARRAY(1,1003,1, 19,2003,3), MDSYS.SDO_ORDINATE_ARRAY(6,15, 10,10, 20,10, 25,15, 25,35, 19,40, 11,40, 6,25, 6,15, 12,15, 15,24)));
The SDO_GEOMETRY object type takes values and constructors for its attributes SDO_GTYPE, SDO_ELEM_INFO, and SDO_ORDINATES. The SDO_GTYPE is 2003, and the SDO_ELEM_INFO has 2 triplet values because there are 2 elements. Element 1 starts at offset 1, is of ETYPE 1003, and its interpretation value is 1 because the points are connected by straight line segments. Element 2 starts at offset 19, is of ETYPE 2003, and has an interpretation value of 3 (a rectangle). The SDO_ORDINATES varying length array has 22 values with SDO_ORDINATES(1...18) describing element 1 and SDO_ORDINATES(19...22) describing element 2.
Assume that two dimensions are named X and Y, their bounds are 0 to 100, and the tolerance for both dimensions is 0.005. The SQL statement for loading the
USER_SDO_GEOM_METADATA metadata view is:
INSERT INTO USER_SDO_GEOM_METADATA VALUES ('PARKS', 'SHAPE', MDSYS.SDO_DIM_ARRAY(MDSYS.SDO_DIM_ELEMENT('X', 0, 100, 0.005), MDSYS.SDO_DIM_ELEMENT('Y', 0, 100, 0.005)), NULL);
A compound line string is a connected sequence of straight line segments and circular arcs. Figure 32 is an example of a compound line string. The coordinate values for points P1..P7 that describe the line string OBJ_2 are:
OBJ_2 = [P1(15,10), P2(25,10), P3(30,5), P4(38,5), P5(38,10),
P6(35,15), P7(25,20)]
The SQL statement for inserting this compound line string in a feature table defined as ROADS(GID Varchar2(32), Shape MDSYS.SDO_GEOMETRY) is:
INSERT INTO ROADS VALUES ('OBJ_2', MDSYS.SDO_GEOMETRY(2002, NULL, NULL, MDSYS.SDO_ELEM_INFO_ARRAY(1,4,2, 1,2,1, 9,2,2), MDSYS.SDO_ORDINATE_ARRAY(15,10, 25,10, 30,5, 38,5, 38,10, 35,15, 25,20)));
The SDO_GEOMETRY object type takes values and constructors for its attributes SDO_GTYPE, SDO_ELEM_INFO, and SDO_ORDINATES. The SDO_GTYPE is 2002, and the SDO_ELEM_INFO_ARRAY has 9 values because there are 2 subelements for the compound line string. The first subelement starts at offset 1, is of SDO_ETYPE 2, and its interpretation value is 1 because the points are connected by straight line segments. Similarly, subelement 2 has a starting offset of 9. That is, the first ordinate value is SDO_ORDINATES(9), is of SDO_ETYPE 2, and has an interpretation value of 2 because the points describe a circular arc. The SDO_ORDINATES_ARRAY varying length array has 14 values, with SDO_ORDINATES(1..10) describing subelement 1, and SDO_ORDINATES(9..14) describing subelement 2.
Assume that two dimensions are named X and Y, their bounds are 0 to 100, and tolerance for both dimensions is 0.005. The SQL statement to insert the metadata into the USER_SDO_GEOM_METADATA view is:
INSERT INTO USER_SDO_GEOM_METADATA VALUES ('ROADS', 'SHAPE',
MDSYS.SDO_DIM_ARRAY(MDSYS.SDO_DIM_ELEMENT('X', 0, 100, 0.005), MDSYS.SDO_DIM_ELEMENT('Y', 0, 100, 0.005)), NULL);
A compound polygon's boundary is a connected sequence of straight line segments and circular arcs, whose first point is equal to its last point. Figure 33 is an example of a compound polygon. The coordinate values for points P1 to P8 that describe the polygon OBJ_3 are:
OBJ_3 = [P1(20,30), P2(11,30), P3(7,22), P4(7,15), P5(11,10), P6(21,10),
P7(27,30), P8(25,27), P1(20,30)]
This example assumes the Parks table was created as follows:
CREATE TABLE PARKS (GID VARCHAR2(32), SHAPE MSSYS.SDO_GEOMETRY);
The SQL statement for inserting this compound polygon is:
INSERT INTO PARKS VALUES ('OBJ_3', MDSYS.SDO_GEOMETRY(2003, NULL,NULL, MDSYS.SDO_ELEM_INFO_ARRAY(1,1005,2, 1,2,1, 13,2,2), MDSYS.SDO_ORDINATE_ARRAY(20,30, 11,30, 7,22, 7,15, 11,10, 21,10, 27,30, 25,27, 20,30)));
The SDO_GEOMETRY object type takes values and constructors for its attributes SDO_GTYPE, SDO_ELEM_INFO, and SDO_ORDINATES. The SDO_GTYPE is 3, the SDO_ELEM_INFO has 3 triplet values. The first triplet (1,5,2) identifies the element as a compound polygon (ETYPE 5) with two subelements. The first subelement starts at offset 1, is of ETYPE 2, and its interpretation value is 1 because the points are connected by straight line segments. Subelement 2 has a starting offset of 13, is of ETYPE 2, and has an interpretation value of 2 because the points describe a circular arc. The SDO_ORDINATES varying length array has 18 values, with SDO_ORDINATES(1...14) describing subelement 1, and SDO_ORDINATES(13...18) describing subelement 2.
This example assumes the Parks table was created as follows:
CREATE TABLE PARKS (GID VARCHAR2(32), SHAPE MSSYS.SDO_GEOMETRY);
Assume that two dimensions are named X and Y, their bounds are 0 to 100, and tolerance for both dimensions is 0.005. The SQL statement to insert the metadata into the USER_SDO_GEOM_METADATA view is:
INSERT INTO USER_SDO_GEOM_METADATA VALUES ('PARKS', 'SHAPE', MDSYS.SDO_DIM_ARRAY(MDSYS.SDO_DIM_ELEMENT('X', 0, 100, 0.005), MDSYS.SDO_DIM_ELEMENT('Y', 0, 100, 0.005)), NULL);
A compound polygon's boundary is a connected sequence of straight line segments and circular arcs. Figure 34 is an example of a geometry that contains a compound polygon with a hole (or void). The coordinate values for points P1 to P8 (Element 1) and C1 to C3 (Element 2) that describe the geometry OBJ_4 are:
Element 1 = [P1(20,30), P2(11,30), P3(7,22), P4(7,15), P5(11,10), P6(21,10), P7(27,30), P8(25,27), P1(20,30)] Element 2 = [C1(10,17), C2(15,22), C3(20,17)]
This example assumes the table Parks has been created as follows:
CREATE TABLE PARKS (GID VARCHAR2(32), SHAPE MSSYS.SDO_GEOMETRY);
The SQL statement for inserting this compound polygon with holes is:
INSERT INTO Parks VALUES ('OBJ_4', MDSYS.SDO_GEOMETRY(2003, NULL,NULL, MDSYS.SDO_ELEM_INFO_ARRAY(1,1005,2, 1,2,1, 13,2,2, 19,2003,4), MDSYS.SDO_ORDINATE_ARRAY(20,30, 11,30, 7,22, 7,15, 11,10, 21,10, 27,30, 25,27, 20,30, 10,17, 15,22, 20,17)));
The SDO_GEOMETRY object type takes values and constructors for its attributes SDO_GTYPE, SDO_ELEM_INFO, and SDO_ORDINATES. The SDO_GTYPE is 2003, the SDO_ELEM_INFO has 4 triplet values. The first 3 triplet values represent element 1. The first triplet (1,5,2) identifies this element as a compound element with two subelements. The values in SDO_ELEM_INFO(1...9) pertain to element 1, while SDO_ELEM_INFO(10...12) are for element 2.
The first subelement starts at offset 1, is of ETYPE 2, and its interpretation is 1 because the points are connected by straight line segments. Subelement 2 has a starting offset of 13, is of ETYPE 2, and has an interpretation value of 2 because the points describe a circular arc. The fourth triplet (19,3,4) represents element 2. Element 2 starts at offset 19, is of ETYPE 3, and its interpretation value is 4, indicating that it is a circle. The SDO_ORDINATES varying length array has 24 values, with SDO_ORDINATES(1...14) describing subelement 1, SDO_ORDINATES(13...18) describing subelement 2, and SDO_ORDINATES(19...24) describing element 2.
Assume that two dimensions are named X and Y, their bounds are 0 to 100, and tolerance for both dimensions is 0.005. The SQL statement to insert the metadata into the USER_SDO_GEOM_METADATA view is:
INSERT INTO USER_SDO_GEOM_METADATA VALUES ('PARKS', 'SHAPE',
MDSYS.SDO_DIM_ARRAY(MDSYS.SDO_DIM_ELEMENT('X', 0, 100, 0.005), MDSYS.SDO_DIM_ELEMENT('Y', 0, 100, 0.005)), NULL);
A pointonly geometry can be inserted with the following statement:
INSERT INTO PARKS VALUES ('OBJ_PT', MDSYS.SDO_GEOMETRY(2001,NULL, MDSYS.SDO_POINT_TYPE(20,30,NULL), NULL, NULL) );
Once data has been loaded into the spatial tables through either bulk or transactional loading, a spatial index must be created on the tables for efficient access to the data. This is done by approximating geometries with tiles. For each geometry, you will have a set of tiles that fully covers the geometry.
Spatial provides two methods for spatial indexing, fixed and hybrid. Hybrid indexing is recommended for the Spatial objectrelational model. If specified correctly, it will provide better selectivity and spatial join performance for most data sets and application scenarios.
The tessellation algorithm used by the CREATE INDEX statement and by index maintenance routines on insert or update operations is determined by the SDO_LEVEL and SDO_NUMTILES values, which are supplied in the PARAMETERS clause of the CREATE INDEX statement. They are interpreted as follows:
An explicit commit operation is executed after the tessellation of all the geometries in a geometry column.
By default, spatial index creation requires a sizable amount of rollback space. To reduce the amount of rollback space required you can supply the SDO_COMMIT_INTERVAL parameter in the CREATE INDEX statement. This will perform a database commit after every n geometries are indexed, where n is a userdefined value.
If the index creation does not complete for any reason, the index is invalid and must be deleted with the DROP INDEX <index_name> [FORCE] statement.
Oracle recommends using hybrid indexing when indexing a geometry using the objectrelational model. Because fixed indexing is an integral part of hybrid indexing, it is important to understand the information in this section. Hybrid indexing is discussed in Section 3.2.3.
While not the preferred method, you can use fixedsize tiles to index the objectrelational model. The fixedsize tile algorithm is expressed as a level referring to the number of tessellations performed. To use fixedsize tile indexing, omit the SDO_NUMTILES parameter and set the SDO_LEVEL value to the desired tiling level. The relationship between the tiling level and the resulting size of the tiles depends on the domain of the layer.
The domain used for indexing is defined by the upper and lower boundaries of each dimension stored in the DIMINFO column of the USER_SDO_GEOM_METADATA view, which contains an entry for the table and geometry column to spatially index. A typical domain could be 180 to 180 degrees for longitude^{1}, and 90 to 90 degrees for latitude, as represented in Figure 35.
If the SDO_LEVEL column is set to 1, then the tiles created by the indexing mechanism are the same size as tiles at the first level of tessellation. Each tile would be 180 degrees by 90 degrees as shown in Figure 36.
The formula for the number of fixedsize tiles in a domain is 4^{n} where n is the number of tessellations, stored in the SDO_LEVEL column. In reality, tiles are only generated where geometries exist, and not necessarily for the whole domain. Figure 37 shows fixedsize tiling at level 2. In this figure, each tile is 90 degrees by 45 degrees.
The size of a tile can be determined by applying the following formula to each dimension:
length = (upper_bound  lower_bound) / 2 ^ sdo_level
The length refers to the length of the tile along the specified dimension. Applying this formula to the tiling shown in Figure 37 yields the following sizes:
length for dimension X = (180  (180) ) / 2^2 = (360) / 4 = 90 length for dimension Y = (90  (90) ) / 2^2 = (180) / 4 = 45
At level 2, the tiles are 90 degrees by 45 degrees in size. As the number of levels increases, the tiles become smaller and smaller. Smaller tiles provide a more precise fit of the tiles over the geometry being indexed. However, because the number of tiles generated is unbounded, you must take into account the performance implications of using higher levels. The SDO_TUNE.ESTIMATE_TILING_LEVEL function can be used to determine an appropriate level for indexing with fixedsize tiles. See Chapter 14 for a description of this function.
Besides the performance aspects related to selecting a fixedsize tile, tessellating the geometry into fixedsize tiles might have benefits related to the type of data being stored, such as using tiles sized to represent 1acre farm plots, city blocks, or individual pixels on a display. Data modeling is an important part of any database design, and is essential in a spatial database where the data often represents actual physical locations.
In Example 33, assume that data has been loaded into a table called Roads, and the USER_SDO_GEOM_METADATA view has an entry for ROADS.SHAPE. You can use the following SQL statement to create a fixed index named ROADS_FIXED.
CREATE INDEX ROADS_FIXED ON ROADS(SHAPE) INDEXTYPE IS MDSYS.SPATIAL_INDEX PARAMETERS('SDO_LEVEL=8');
The value in SDO_LEVEL is used while tessellating objects. Increasing the level results in smaller tiles and better geometry approximations. See the description of the ESTIMATE_TILING_LEVEL function in Chapter 14 for information on estimating the tiling level in several different ways.
This section describes hybrid indexing, which uses both fixedsize and variablesized tiles as a spatial indexing mechanism. For each geometry, you will have a set of fixedsize tiles that fully covers the geometry, and a set of variablesized tiles that fully covers the geometry.The terms hybrid indexing, hybrid tiling, and hybrid tessellation are used interchangeably in this section.
To use hybrid tiling, the SDO_LEVEL and SDO_NUMTILES keywords in the PARAMETERS clause must contain valid values. Both SDO_LEVEL and SDO_NUMTILES must be greater than 1.
The SDO_NUMTILES value determines the number of variable tiles that will be used to fully cover a geometry being indexed. Typically this value is small. For points, SDO_NUMTILES is always one. For other element types, you might set SDO_NUMTILES to a value around 8. The larger the SDO_NUMTILES parameter, the better the tiles will approximate the geometry being covered. This improves the selectivity of the primary filter, but also increases the number of index entries per geometry (see Section 4.2.1 and Section 4.2.2 for a discussion of primary and secondary filters). The SDO_NUMTILES value should be larger for long, linear spatial entities, such as major highways or rivers, than for arearelated spatial entities such as county or state boundaries.
The SDO_LEVEL value determines the size of the fixed tiles used to fully cover the geometry being indexed. Setting the proper SDO_LEVEL value may appear more like art than science. Performing some simple data analysis and testing puts the process back in the realm of science. One approach would be to use the SDO_TUNE.ESTIMATE_TILING_LEVEL function to determine an appropriate starting SDO_LEVEL value, and then compare the performance with slightly higher or lower values. This, and other techniques, are described in Appendix A, "Tuning Tips and Sample SQL Scripts".
In Example 34, assume that data has been loaded into a table called Roads, and the USER_SDO_GEOM_METADATA view has an entry for ROADS.SHAPE. (Assume also that no spatial index has already been created on the ROADS.SHAPE column.) You can use the following SQL statement to create a hybrid index named ROADS_HYBRID.
CREATE INDEX ROADS_HYBRID ON ROADS(SHAPE) INDEXTYPE IS MDSYS.SPATIAL_INDEX PARAMETERS('SDO_LEVEL=6 SDO_NUMTILES=12');
You can create a spatial index on a table that is not in your schema. Assume that user B wants to create a spatial index on column geometry in table T1 under user A's schema. User B must perform the following steps:
GRANT select on T1 to B;
GRANT create table to A; CREATE INDEX qtree on B.T1(geometry) INDEXTYPE IS mdsys.spatial_index PARAMETERS('sdo_level=10 sdo_numtiles=4');
^{1}
The transference of the domain onto a sphere or Mercator projection is left up to an application. Spatial treats the domain as a flat Cartesian grid.

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