Release 2 (9.2)
Part Number A96595-01
 Home |
 Book List |
 Contents |
 Index |
 Master Index |
 Feedback |
| Oracle9i Data Cartridge Developer's Guide Release 2 (9.2) Part Number A96595-01 |
|
This chapter explains the power demand sample data cartridge that is discussed throughout this book. The power demand cartridge includes a user-defined object type, extensible indexing, and optimization. This chapter covers the following topics:
This chapter does not explain in detail the concepts related to the features illustrated. For information about extensible indexing, see Chapter 7, "Building Domain Indexes". For information about extensible query optimization, see Chapter 8, "Query Optimization". For information about cartridge services, see Chapter 9, "Using Cartridge Services".
This chapter divides the example into segments and provides commentary. The entire cartridge definition is available online in file extdemo1.sql in the Oracle demo directory.
A power utility, Power-To-The-People, develops a sophisticated model to decide how to deploy its resources. The region served by the utility is represented by a grid laid over a geographic area.
This region may be surrounded by other regions some of whose power needs are supplied by other utilities. As pictured, every region is composed of geographic quadrants referred to as "cells" on a 10x10 grid. There are a number of ways of identifying cells -- by spatial coordinates (longitude/latitude), by a matrix numbering (1,1; 1,2;...), and by numbering them sequentially:
Within the area represented by each cell, the power used by consumers in that area is recorded each hour. For example, the power demand readings for a particular hour might be represented by Table 13-1 (cells here represented on a matrix):
The power stations also receives reports from two other sources:
By analyzing the correlation between historical power demand from cells and the temperature readings for those regions, the utility is able to determine with a close approximation what the demand will be, given specific temperatures.
These images are designed so that 'lighter is colder'. Thus, the image shows a cold front moving into the region from the south-west. By correlating the data provided by the grayscale images with temperature readings taken at the same time, the utility has been able to determine what the power demand is given weather conditions viewed from the stratosphere.
The reason that this is important is that a crucial part of this modeling has to do with noting the rapidity and degree of change in the incoming reports as weather changes and power is deployed. The following diagram shows same cold front at a second recording:
By analyzing the extent and speed of the cold front, the utility is able to project what the conditions are likely to be in the short and medium term:
By combing this data about these conditions, and other anomalous situations (such as the failure of a substation) the utility must be able to organize the most optimal deployment of its resources. The following drawing reflects the distribution of substations across the region:
The distribution of power stations means that the utility can redirect its deployment of electricity to the areas of greatest need. The following figure gives a pictorial representation of the overlap between three stations:
Depending on fluctuating requirements, the utility must be able to decide how to deploy its resources, and even whether to purchase power from a neighboring utility in the event of shortfall.
The following Class Diagram describes the application objects using the Unified Modelling Language (UML) notation.
Modelling the application in this way, makes possible the following specific queries:
These queries are, of course, only a short list of the possible information that could be gleaned from the system. For instance, it is obvious that the developer of such an application would want to build queries that are based on the information derived from prior queries:
The Power Demand cartridge as implemented is described in the following class diagram.
The utility gets ongoing reports from weather centers about current conditions and from power stations about ongoing power utilization for specific geographical areas (represented by cells on a 10x10 grid). It then compares this information to historical data in order to predict demand for power in the different geographic areas for given time periods.
Each service area for the utility is considered as a 10x10 grid of cells, where each cell's boundaries are associated with spatial coordinates (longitude/latitude). The geographical areas represented by the cells can be uniform or can have different shapes and sizes. Within the area represented by each cell, the power used by consumers in that area is recorded each hour. For example, the power demand readings for a particular hour might be represented by Table 13-2.
The numbers in each cell reflect power demand (in some unit of measurement determined by the electric utility) for the hour for that area. For example, the demand for the first cell (1,1) was 23, the demand for the second cell (1,2) was 21, and so on. The demand for the last cell (10, 10) was 32.
The utility uses this data for many monitoring and analytical applications. Readings for individual cells are monitored for unusual surges or decreases in demand. For example, the readings of 98 for (6,3) and 87 for (8,1) might be unusually high, and the readings of 19 for (4,7) and 12 for (10,4) might be unusually low. Trends are also analyzed, such as significant increases or decreases in demand for each neighborhood, for each station, and overall, over time.
Before you use extensible indexing, you should first ask whether the users of the table will benefit from having the domain index. That is, will they execute queries that could run just as efficiently using a standard Oracle index, or using no index at all.
A query does not require a domain index if both of the following are true:
equals, lessthan, greaterthan, max, and min for a b-tree index.In the PowerDemand_Typ object type cartridge example, the values for three columns (TotGridDemand, MaxCellDemand, and MinCellDemand) are set by functions, after which the values do not change. (For example, the total grid power demand for 13:00 on 01-Jan-1998 does not change after it has been computed.) For queries that use these columns, a standard b-tree index on each column is sufficient and recommended for operations like equals, lessthan, greaterthan, max, and min.
Examples of queries that would not benefit from extensible indexing (using the power demand cartridge) include:
To make this query run efficiently, define two additional columns in the PowerDemand_Typ object type (AverageCellDemand and MedianCellDemand), and create functions to set the values of these columns. (For example, AverageCellDemand is TotGridDemand divided by 100.) Then, create b-tree indexes on the AverageCellDemand and MedianCellDemand columns.
A query benefits from a domain index if the data being queried against cannot be made a simple attribute of a table or if the operation to be performed on the data is not one of the standard operations supported by Oracle indexes.
Examples of queries that would benefit from extensible indexing (using the power demand cartridge) include:
By asking for the first cell, the query goes beyond a simple true-false check (such as finding out whether any cell for a specified time had a demand equal to a specified value), and thus benefits from a domain index.
This section explains the parts of the power demand cartridge as they relate to extensible indexing. Explanatory text and code segments are mixed.
The entire cartridge definition is available online as extdemo1.sql in the standard Oracle demo directory (location is platform-dependent).
Before you create a domain index, create a database user (schema) to own the index. In the power demand example, the user PowerCartUser is created and granted the appropriate privileges. All database structures related to the cartridge are created under this user (that is, while the cartridge developer or DBA is connected to the database as PowerCartUser).
set echo on connect sys/knl_test7 as sysdba; drop user PowerCartUser cascade; create user PowerCartUser identified by PowerCartUser; ------------------------------------------------------------------- -- INITIAL SET-UP ------------------------------------------------------------------- -- grant privileges -- grant connect, resource to PowerCartUser; -- do we need to grant these privileges -- grant create operator to PowerCartUser; grant create indextype to PowerCartUser; grant create table to PowerCartUser;
The object type PowerDemand_Typ is used to store the hourly power grid readings. This type is used to define a column in the table in which the readings are stored.
First, two types are defined for later use:
PowerGrid_Typ, to define the cells in PowerDemand_TypNumTab_Typ, to be used in the table in which the index entries are stored
CREATE OR REPLACE TYPE PowerGrid_Typ as VARRAY(100) of NUMBER; CREATE OR REPLACE TYPE NumTab_Typ as TABLE of NUMBER;
The PowerDemand_Typ type includes:
TotGridDemand, MaxCellDemand, MinCellDemand) that are set by three member proceduresCREATE OR REPLACE TYPE PowerDemand_Typ AS OBJECT ( -- Total power demand for the grid TotGridDemand NUMBER, -- Cell with maximum/minimum power demand for the grid MaxCellDemand NUMBER, MinCellDemand NUMBER, -- Power grid: 10X10 array represented as Varray(100) -- using previously defined PowerGrid_Typ CellDemandValues PowerGrid_Typ, -- Date/time for power-demand samplings: Every hour, -- 100 areas transmit their power demand readings. SampleTime DATE, -- -- Methods (Set...) for this type: -- Total demand for the entire power grid for a -- SampleTime: sets the value of TotGridDemand. Member Procedure SetTotalDemand, -- Maximum demand for the entire power grid for a -- SampleTime: sets the value of MaxCellDemand. Member Procedure SetMaxDemand, -- Minimum demand for the entire power grid for a -- SampleTime: sets the value of MinCellDemand. Member Procedure SetMinDemand ); /
The PowerDemand_Typ object type has methods that set the first three attributes in the type definition:
TotGridDemand, the total demand for the entire power grid for the hour in question (identified by SampleTime)MaxCellDemand, the highest power demand value for all cells for the SampleTimeMinCellDemand, the lowest power demand value for all cells for the SampleTimeThe logic for each procedure is not complicated. SetTotDemand loops through the cell values and creates a running total. SetMaxDemand compares the first two cell values and saves the higher as the current highest value; it then examines each successive cell, comparing it against the current highest value and saving the higher of the two as the current highest value, until it reaches the end of the cell values. SetMinDemand uses the same approach as SetMaxDemand, but it continually saves the lower value in comparisons to derive the lowest value overall.
CREATE OR REPLACE TYPE BODY PowerDemand_Typ IS -- -- Methods (Set...) for this type: -- Total demand for the entire power grid for a -- SampleTime: sets the value of TotGridDemand. Member Procedure SetTotalDemand IS I BINARY_INTEGER; Total NUMBER; BEGIN Total :=0; I := CellDemandValues.FIRST; WHILE I IS NOT NULL LOOP Total := Total + CellDemandValues(I); I := CellDemandValues.NEXT(I); END LOOP; TotGridDemand := Total; END; -- Maximum demand for the entire power grid for a -- SampleTime: sets the value of MaxCellDemand. Member Procedure SetMaxDemand IS I BINARY_INTEGER; Temp NUMBER; BEGIN I := CellDemandValues.FIRST; Temp := CellDemandValues(I); WHILE I IS NOT NULL LOOP IF Temp < CellDemandValues(I) THEN Temp := CellDemandValues(I); END IF; I := CellDemandValues.NEXT(I); END LOOP; MaxCellDemand := Temp; END; -- Minimum demand for the entire power grid for a -- SampleTime: sets the value of MinCellDemand. Member Procedure SetMinDemand IS I BINARY_INTEGER; Temp NUMBER; BEGIN I := CellDemandValues.FIRST; Temp := CellDemandValues(I); WHILE I IS NOT NULL LOOP IF Temp > CellDemandValues(I) THEN Temp := CellDemandValues(I); END IF; I := CellDemandValues.NEXT(I); END LOOP; MinCellDemand := Temp; END; END; /
The power demand cartridge is designed so that users can query the power grid for relationships of equality, greaterthan, or lessthan. However, because of the way the cell demand data is stored, the standard operators (=, >, <) cannot be used. Instead, new operators must be created, and a function must be created to define the implementation for each new operator (that is, how the operator is to be interpreted by Oracle).
For this cartridge, each of the three relationships can be checked in two ways:
These operators have names in the form Power_XxxxxSpecific (such as Power_EqualsSpecific), and the implementing functions have names in the form Power_XxxxxSpecific_Func.
These operators have names in the form Power_XxxxxAny (such as Power_EqualsAny), and the implementing functions have names in the form Power_XxxxxAny_Func.
For each operator-function pair, the function is defined first and then the operator as using the function. The function is the implementation that would be used if there were no index defined. This implementation must be specified so that the Oracle optimizer can determine costs, decide whether the index should be used, and create an execution plan.
Table 13-3 shows the operators and implementing functions:
Each function and operator returns a numeric value of 1 if the condition is true (for example, if the specified cell is equal to the specified value), 0 if the condition is not true, or null if the specified cell number is invalid.
The following statements create the implementing functions (Power_xxx_Func), first the specific and then the any implementations.
CREATE FUNCTION Power_EqualsSpecific_Func( object PowerDemand_Typ, cell NUMBER, value NUMBER) RETURN NUMBER AS BEGIN IF cell <= object.CellDemandValues.LAST THEN IF (object.CellDemandValues(cell) = value) THEN RETURN 1; ELSE RETURN 0; END IF; ELSE RETURN NULL; END IF; END; / CREATE FUNCTION Power_GreaterThanSpecific_Func( object PowerDemand_Typ, cell NUMBER, value NUMBER) RETURN NUMBER AS BEGIN IF cell <= object.CellDemandValues.LAST THEN IF (object.CellDemandValues(cell) > value) THEN RETURN 1; ELSE RETURN 0; END IF; ELSE RETURN NULL; END IF; END; / CREATE FUNCTION Power_LessThanSpecific_Func( object PowerDemand_Typ, cell NUMBER, value NUMBER) RETURN NUMBER AS BEGIN IF cell <= object.CellDemandValues.LAST THEN IF (object.CellDemandValues(cell) < value) THEN RETURN 1; ELSE RETURN 0; END IF; ELSE RETURN NULL; END IF; END; / CREATE FUNCTION Power_EqualsAny_Func( object PowerDemand_Typ, value NUMBER) RETURN NUMBER AS idx NUMBER; BEGIN FOR idx IN object.CellDemandValues.FIRST..object.CellDemandValues.LAST LOOP IF (object.CellDemandValues(idx) = value) THEN RETURN 1; END IF; END LOOP; RETURN 0; END; / CREATE FUNCTION Power_GreaterThanAny_Func( object PowerDemand_Typ, value NUMBER) RETURN NUMBER AS idx NUMBER; BEGIN FOR idx IN object.CellDemandValues.FIRST..object.CellDemandValues.LAST LOOP IF (object.CellDemandValues(idx) > value) THEN RETURN 1; END IF; END LOOP; RETURN 0; END; / CREATE FUNCTION Power_LessThanAny_Func( object PowerDemand_Typ, value NUMBER) RETURN NUMBER AS idx NUMBER; BEGIN FOR idx IN object.CellDemandValues.FIRST..object.CellDemandValues.LAST LOOP IF (object.CellDemandValues(idx) < value) THEN RETURN 1; END IF; END LOOP; RETURN 0; END; /
The following statements create the operators (Power_xxx). Each statement specifies an implementing function.
CREATE OPERATOR Power_Equals BINDING(PowerDemand_Typ, NUMBER, NUMBER) RETURN NUMBER USING Power_EqualsSpecific_Func; CREATE OPERATOR Power_GreaterThan BINDING(PowerDemand_Typ, NUMBER, NUMBER) RETURN NUMBER USING Power_GreaterThanSpecific_Func; CREATE OPERATOR Power_LessThan BINDING(PowerDemand_Typ, NUMBER, NUMBER) RETURN NUMBER USING Power_LessThanSpecific_Func; CREATE OPERATOR Power_EqualsAny BINDING(PowerDemand_Typ, NUMBER) RETURN NUMBER USING Power_EqualsAny_Func; CREATE OPERATOR Power_GreaterThanAny BINDING(PowerDemand_Typ, NUMBER) RETURN NUMBER USING Power_GreaterThanAny_Func; CREATE OPERATOR Power_LessThanAny BINDING(PowerDemand_Typ, NUMBER) RETURN NUMBER USING Power_LessThanAny_Func;
The power demand cartridge creates an object type for the indextype that specifies methods for the domain index. These methods are part of the ODCIIndex (Oracle Data Cartridge Interface Index) interface, and they collectively define the behavior of the index in terms of the methods for defining, manipulating, scanning, and exporting the index.
Table 13-4 shows the method functions (all but one starting with ODCIIndex) created for the power demand cartridge.
The following statement creates the power_idxtype_im object type. The methods of this type are the ODCI methods to define, manipulate, and scan the domain index. The curnum attribute is the cursor number used as context for the scan routines (ODCIIndexStart, ODCIIndexFetch, and ODCIIndexClose).
CREATE OR REPLACE TYPE power_idxtype_im AS OBJECT ( curnum NUMBER, STATIC FUNCTION ODCIGetInterfaces(ifclist OUT sys.ODCIObjectList) RETURN NUMBER, STATIC FUNCTION ODCIIndexCreate (ia sys.ODCIIndexInfo, parms VARCHAR2, env sys.ODCIEnv) RETURN NUMBER, STATIC FUNCTION ODCIIndexDrop(ia sys.ODCIIndexInfo, env sys.ODCIEnv) RETURN NUMBER, STATIC FUNCTION ODCIIndexStart(sctx IN OUT power_idxtype_im, ia sys.ODCIIndexInfo, op sys.ODCIPredInfo, qi sys.ODCIQueryInfo, strt NUMBER, stop NUMBER, cmppos NUMBER, cmpval NUMBER, env sys.ODCIEnv) RETURN NUMBER, STATIC FUNCTION ODCIIndexStart(sctx IN OUT power_idxtype_im, ia sys.ODCIIndexInfo, op sys.ODCIPredInfo, qi sys.ODCIQueryInfo, strt NUMBER, stop NUMBER, cmpval NUMBER, env sys.ODCIEnv) RETURN NUMBER, MEMBER FUNCTION ODCIIndexFetch(nrows NUMBER, rids OUT sys.ODCIRidList, env sys.ODCIEnv) RETURN NUMBER, MEMBER FUNCTION ODCIIndexClose (env sys.ODCIEnv) RETURN NUMBER, STATIC FUNCTION ODCIIndexInsert(ia sys.ODCIIndexInfo, rid VARCHAR2, newval PowerDemand_Typ, env sys.ODCIEnv) RETURN NUMBER, STATIC FUNCTION ODCIIndexDelete(ia sys.ODCIIndexInfo, rid VARCHAR2, oldval PowerDemand_Typ, env sys.ODCIEnv) RETURN NUMBER, STATIC FUNCTION ODCIIndexUpdate(ia sys.ODCIIndexInfo, rid VARCHAR2, oldval PowerDemand_Typ, newval PowerDemand_Typ, env sys.ODCIEnv) RETURN NUMBER, STATIC FUNCTION ODCIIndexGetMetadata(ia sys.ODCIIndexInfo, expversion VARCHAR2, newblock OUT PLS_INTEGER, env sys.ODCIEnv) RETURN VARCHAR2 ); /
The CREATE TYPE statement is followed by a CREATE TYPE BODY statement that specifies the implementation for each member function:
CREATE OR REPLACE TYPE BODY power_idxtype_im IS ...
Each type method is described in a separate section, but the method definitions (except for ODCIIndexGetMetadata, which returns a VARCHAR2 string) have the following general form:
STATIC FUNCTION function-name (...) RETURN NUMBER IS ... END;
The ODCIGetInterfaces function returns the list of names of the interfaces implemented by the type. To specify the Oracle9i version of these interfaces, the ODCIGetInterfaces routine must return 'SYS.ODCIINDEX2' in the OUT parameter.
STATIC FUNCTION ODCIGetInterfaces(ifclist OUT sys.ODCIObjectList) RETURN NUMBER IS BEGIN ifclist := sys.ODCIObjectList(sys.ODCIObject('SYS','ODCIINDEX2')); return ODCIConst.Success; END ODCIGetInterfaces;
The ODCIIndexCreate function creates the table to store index data. If the base table containing data to be indexed is not empty, this method inserts the index data entries for existing data.
The function takes the index information as an object parameter whose type is SYS.ODCIINDEXINFO. The type attributes include the index name, owner name, and so forth. The PARAMETERS string specified in the CREATE INDEX statement is also passed in as a parameter to the function.
STATIC FUNCTION ODCIIndexCreate (ia sys.ODCIIndexInfo, parms VARCHAR2, env sys.ODCIEnv) RETURN NUMBER IS i INTEGER; r ROWID; p NUMBER; v NUMBER; stmt1 VARCHAR2(1000); stmt2 VARCHAR2(1000); stmt3 VARCHAR2(1000); cnum1 INTEGER; cnum2 INTEGER; cnum3 INTEGER; junk NUMBER;
The SQL statement to create the table for the index data is constructed and executed. The table includes the ROWID of the base table (r), the cell position number (cpos) in the grid from 1 to 100, and the power demand value in that cell (cval).
BEGIN -- Construct the SQL statement. stmt1 := 'CREATE TABLE ' || ia.IndexSchema || '.' || ia.IndexName || '_pidx' || '( r ROWID, cpos NUMBER, cval NUMBER)'; -- Dump the SQL statement. dbms_output.put_line('ODCIIndexCreate>>>>>'); sys.ODCIIndexInfoDump(ia); dbms_output.put_line('ODCIIndexCreate>>>>>'||stmt1); -- Execute the statement. cnum1 := dbms_sql.open_cursor; dbms_sql.parse(cnum1, stmt1, dbms_sql.native); junk := dbms_sql.execute(cnum1); dbms_sql.close_cursor(cnum1);
The function populates the index by inserting rows into the table. The function "unnests" the VARRAY attribute and inserts a row for each cell into the table. Thus, each 10 X 10 grid (10 rows, 10 values for each row) becomes 100 rows in the table (one row for each cell).
-- Now populate the table. stmt2 := ' INSERT INTO '|| ia.IndexSchema || '.' || ia.IndexName || '_pidx' || ' SELECT :rr, ROWNUM, column_value FROM THE' || ' (SELECT CAST (P.'|| ia.IndexCols(1).ColName||'.CellDemandValues AS NumTab_Typ)'|| ' FROM ' || ia.IndexCols(1).TableSchema || '.' || ia.IndexCols(1).TableName || ' P' || ' WHERE P.ROWID = :rr)'; -- Execute the statement. dbms_output.put_line('ODCIIndexCreate>>>>>'||stmt2); -- Parse the statement. cnum2 := dbms_sql.open_cursor; dbms_sql.parse(cnum2, stmt2, dbms_sql.native); stmt3 := 'SELECT ROWID FROM '|| ia.IndexCols(1).TableSchema || '.' || ia.IndexCols(1).TableName; dbms_output.put_line('ODCIIndexCreate>>>>>'||stmt3); cnum3 := dbms_sql.open_cursor; dbms_sql.parse(cnum3, stmt3, dbms_sql.native); dbms_sql.define_column_rowid(cnum3, 1, r); junk := dbms_sql.execute(cnum3); WHILE dbms_sql.fetch_rows(cnum3) > 0 LOOP -- Get column values of the row. -- dbms_sql.column_value_rowid(cnum3, 1, r); -- Bind the row into the cursor for the next insert. -- dbms_sql.bind_variable_rowid(cnum2, ':rr', r); junk := dbms_sql.execute(cnum2); END LOOP;
The function concludes by closing the cursors and returning a success status.
dbms_sql.close_cursor(cnum2); dbms_sql.close_cursor(cnum3); RETURN ODCICONST.SUCCESS; END;
The ODCIIndexDrop function drops the table that stores the index data. This method is called when a DROP INDEX statement is issued.
STATIC FUNCTION ODCIIndexDrop(ia sys.ODCIIndexInfo, env sys.ODCIEnv) RETURN NUMBER IS stmt VARCHAR2(1000); cnum INTEGER; junk INTEGER; BEGIN -- Construct the SQL statement. stmt := 'drop table ' || ia.IndexSchema || '.' || ia.IndexName || '_pidx'; dbms_output.put_line('ODCIIndexDrop>>>>>'); sys.ODCIIndexInfoDump(ia); dbms_output.put_line('ODCIIndexDrop>>>>>'||stmt); -- Execute the statement. cnum := dbms_sql.open_cursor; dbms_sql.parse(cnum, stmt, dbms_sql.native); junk := dbms_sql.execute(cnum); dbms_sql.close_cursor(cnum); RETURN ODCICONST.SUCCESS; END;
The first definition of the ODCIIndexStart function initializes the scan of the index to return all rows that satisfy the operator predicate. For example, if a query asks for all instances where cell (3,7) has a value equal to 25, the function initializes the scan to return all rows in the index-organized table for which that cell has that value. (This definition of ODCIIndexStart differs from the definition in the next section in that it includes the cmppos parameter for the position of the cell.)
The self parameter is the context that is shared with the ODCIIndexFetch and ODCIIndexClose functions. The ia parameter contains the index information (an object instance of type SYS.ODCIINDEXINFO), and the op parameter contains the operator information (an object instance of type SYS.ODCIOPERINFO). The strt and stop parameters are the lower and upper boundary points for the operator return value. The cmppos parameter is the cell position and cmpval is the value in the cell specified by the operator (Power_XxxxxSpecific).
STATIC FUNCTION ODCIIndexStart(sctx IN OUT power_idxtype_im, ia sys.ODCIIndexInfo, op sys.ODCIPredInfo, qi sys.ODCIQueryInfo, strt NUMBER, stop NUMBER, cmppos NUMBER, cmpval NUMBER, env sys.ODCIEnv ) RETURN NUMBER IS cnum INTEGER; rid ROWID; nrows INTEGER; relop VARCHAR2(2); stmt VARCHAR2(1000); BEGIN dbms_output.put_line('ODCIIndexStart>>>>>'); sys.ODCIIndexInfoDump(ia); sys.ODCIPredInfoDump(op); dbms_output.put_line('start key : '||strt); dbms_output.put_line('stop key : '||stop); dbms_output.put_line('compare position : '||cmppos); dbms_output.put_line('compare value : '||cmpval);
The function checks for errors in the predicate.
-- Take care of some error cases. -- The only predicates in which btree operators can appear are -- op() = 1 OR op() = 0 if (strt != 1) and (strt != 0) then raise_application_error(-20101, 'Incorrect predicate for operator'); END if; if (stop != 1) and (stop != 0) then raise_application_error(-20101, 'Incorrect predicate for operator'); END if;
The function generates the SQL statement to be executed. It determines the operator name and the lower and upper index value bounds (the start and stop keys). The start and stop keys can both be 1 (= TRUE) or both be 0 (= FALSE).
-- Generate the SQL statement to be executed. -- First, figure out the relational operator needed for the statement. -- Take into account the operator name and the start and stop keys. -- For now, the start and stop keys can both be 1 (= TRUE) or -- both be 0 (= FALSE). if op.ObjectName = 'POWER_EQUALS' then if strt = 1 then relop := '='; else relop := '!='; end if; elsif op.ObjectName = 'POWER_LESSTHAN' then if strt = 1 then relop := '<'; else relop := '>='; end if; elsif op.ObjectName = 'POWER_GREATERTHAN' then if strt = 1 then relop := '>'; else relop := '<='; end if; else raise_application_error(-20101, 'Unsupported operator'); end if; stmt := 'select r from '||ia.IndexSchema||'.'||ia.IndexName||'_pidx'|| ' where cpos '|| '=' ||''''||cmppos||''''|| ' and cval '||relop||''''||cmpval||''''; dbms_output.put_line('ODCIIndexStart>>>>>' || stmt); cnum := dbms_sql.open_cursor; dbms_sql.parse(cnum, stmt, dbms_sql.native); dbms_sql.define_column_rowid(cnum, 1, rid); nrows := dbms_sql.execute(cnum);
The function stores the cursor number in the context, which is used by the ODCIIndexFetch function, and sets a success return status.
-- Set context as the cursor number. self := power_idxtype_im(cnum); -- Return success. RETURN ODCICONST.SUCCESS; END;
This definition of the ODCIIndexStart function initializes the scan of the index to return all rows that satisfy the operator predicate. For example, if a query asks for all instances where any cell has a value equal to 25, the function initializes the scan to return all rows in the index-organized table for which that cell has that value. (This definition of ODCIIndexStart differs from the definition in the preceding section in that it does not include the cmppos parameter.)
The self parameter is the context that is shared with the ODCIIndexFetch and ODCIIndexClose functions. The ia parameter contains the index information (an object instance of type SYS.ODCIINDEXINFO), and the op parameter contains the operator information (an object instance of type SYS.ODCIOPERINFO). The strt and stop parameters are the lower and upper boundary points for the operator return value. The cmpval parameter is the value in the cell specified by the operator (Power_Xxxxx).
STATIC FUNCTION ODCIIndexStart(sctx IN OUT power_idxtype_im, ia sys.ODCIIndexInfo, op sys.ODCIPredInfo, qi sys.ODCIQueryInfo, strt NUMBER, stop NUMBER, cmpval NUMBER, env sys.ODCIEnv ) RETURN NUMBER IS cnum INTEGER; rid ROWID; nrows INTEGER; relop VARCHAR2(2); stmt VARCHAR2(1000); BEGIN dbms_output.put_line('ODCIIndexStart>>>>>'); sys.ODCIIndexInfoDump(ia); sys.ODCIPredInfoDump(op); dbms_output.put_line('start key : '||strt); dbms_output.put_line('stop key : '||stop); dbms_output.put_line('compare value : '||cmpval);
The function checks for errors in the predicate.
-- Take care of some error cases. -- The only predicates in which btree operators can appear are -- op() = 1 OR op() = 0 if (strt != 1) and (strt != 0) then raise_application_error(-20101, 'Incorrect predicate for operator'); END if; if (stop != 1) and (stop != 0) then raise_application_error(-20101, 'Incorrect predicate for operator'); END if;
The function generates the SQL statement to be executed. It determines the operator name and the lower and upper index value bounds (the start and stop keys). The start and stop keys can both be 1 (= TRUE) or both be 0 (= FALSE).
-- Generate the SQL statement to be executed. -- First, figure out the relational operator needed for the statement. -- Take into account the operator name and the start and stop keys. -- For now, the start and stop keys can both be 1 (= TRUE) or -- both be 0 (= FALSE). if op.ObjectName = 'POWER_EQUALSANY' then relop := '='; elsif op.ObjectName = 'POWER_LESSTHANANY' then relop := '<'; elsif op.ObjectName = 'POWER_GREATERTHANANY' then relop := '>'; else raise_application_error(-20101, 'Unsupported operator'); end if; -- This statement returns the qualifying rows for the TRUE case. stmt := 'select distinct r from '||ia.IndexSchema||'.'||ia.IndexName|| '_pidx'||' where cval '||relop||''''||cmpval||''''; -- In the FALSE case, we need to find the complement of the rows. if (strt = 0) then stmt := 'select distinct r from '||ia.IndexSchema||'.'|| ia.IndexName||'_pidx'||' minus '||stmt; end if; dbms_output.put_line('ODCIIndexStart>>>>>' || stmt); cnum := dbms_sql.open_cursor; dbms_sql.parse(cnum, stmt, dbms_sql.native); dbms_sql.define_column_rowid(cnum, 1, rid); nrows := dbms_sql.execute(cnum);
The function stores the cursor number in the context, which is used by the ODCIIndexFetch function, and sets a success return status.
-- Set context as the cursor number. self := power_idxtype_im(cnum); -- Return success. RETURN ODCICONST.SUCCESS; END;
The ODCIIndexFetch function returns a batch of ROWIDs for the rows that satisfy the operator predicate. Each time ODCIIndexFetch is invoked, it returns the next batch of rows (rids parameter, a collection of type SYS.ODCIRIDLIST) that satisfy the operator predicate. The maximum number of rows that can be returned on each invocation is specified by the nrows parameter.
Oracle invokes ODCIIndexFetch repeatedly until all rows that satisfy the operator predicate have been returned.
MEMBER FUNCTION ODCIIndexFetch(nrows NUMBER, rids OUT sys.ODCIRidList, env sys.ODCIEnv) RETURN NUMBER IS cnum INTEGER; idx INTEGER := 1; rlist sys.ODCIRidList := sys.ODCIRidList(); done boolean := FALSE;
The function loops through the collection of rows selected by the ODCIIndexStart function, using the same cursor number (cnum) as in the ODCIIndexStart function, and returns the ROWIDs.
BEGIN dbms_output.put_line('ODCIIndexFetch>>>>>'); dbms_output.put_line('Nrows : '||round(nrows)); cnum := self.curnum; WHILE not done LOOP if idx > nrows then done := TRUE; else rlist.extEND; if dbms_sql.fetch_rows(cnum) > 0 then dbms_sql.column_value_rowid(cnum, 1, rlist(idx)); idx := idx + 1; else rlist(idx) := null; done := TRUE; END if; END if; END LOOP; rids := rlist; RETURN ODCICONST.SUCCESS; END;
The ODCIIndexClose function closes the cursor used by the ODCIIndexStart and ODCIIndexFetch functions.
MEMBER FUNCTION ODCIIndexClose (env sys.ODCIEnv) RETURN NUMBER IS cnum INTEGER; BEGIN dbms_output.put_line('ODCIIndexClose>>>>>'); cnum := self.curnum; dbms_sql.close_cursor(cnum); RETURN ODCICONST.SUCCESS; END;
The ODCIIndexInsert function is called when a record is inserted in a table that contains columns or OBJECT attributes indexed by the indextype. The new values in the indexed columns are passed in as arguments along with the corresponding row identifier.
STATIC FUNCTION ODCIIndexInsert(ia sys.ODCIIndexInfo, rid VARCHAR2, newval PowerDemand_Typ, env sys.ODCIEnv) RETURN NUMBER AS cid INTEGER; i BINARY_INTEGER; nrows INTEGER; stmt VARCHAR2(1000); BEGIN dbms_output.put_line(' '); dbms_output.put_line('ODCIIndexInsert>>>>>'|| ' TotGridDemand= '||newval.TotGridDemand || ' MaxCellDemand= '||newval.MaxCellDemand || ' MinCellDemand= '||newval.MinCellDemand) ; sys.ODCIIndexInfoDump(ia); -- Construct the statement. stmt := ' INSERT INTO '|| ia.IndexSchema || '.' || ia.IndexName || '_pidx' ||' VALUES (:rr, :pos, :val)'; -- Execute the statement. dbms_output.put_line('ODCIIndexInsert>>>>>'||stmt); -- Parse the statement. cid := dbms_sql.open_cursor; dbms_sql.parse(cid, stmt, dbms_sql.native); dbms_sql.bind_variable_rowid(cid, ':rr', rid); -- Iterate over the rows of the Varray and insert them. i := newval.CellDemandValues.FIRST; WHILE i IS NOT NULL LOOP -- Bind the row into the cursor for insert. dbms_sql.bind_variable(cid, ':pos', i); dbms_sql.bind_variable(cid, ':val', newval.CellDemandValues(i)); -- Execute. nrows := dbms_sql.execute(cid); dbms_output.put_line('ODCIIndexInsert>>>>>('|| 'RID' ||' , '|| i || ' , '|| newval.CellDemandValues(i)|| ')'); i := newval.CellDemandValues.NEXT(i); END LOOP; dbms_sql.close_cursor(cid); RETURN ODCICONST.SUCCESS; END ODCIIndexInsert;
The ODCIIndexDelete function is called when a record is deleted from a table that contains columns or object attributes indexed by the indextype. The old values in the indexed columns are passed in as arguments along with the corresponding row identifier.
STATIC FUNCTION ODCIIndexDelete(ia sys.ODCIIndexInfo, rid VARCHAR2, oldval PowerDemand_Typ, env sys.ODCIEnv) RETURN NUMBER AS cid INTEGER; stmt VARCHAR2(1000); nrows INTEGER; BEGIN dbms_output.put_line(' '); dbms_output.put_line('ODCIIndexDelete>>>>>'|| ' TotGridDemand= '||oldval.TotGridDemand || ' MaxCellDemand= '||oldval.MaxCellDemand || ' MinCellDemand= '||oldval.MinCellDemand) ; sys.ODCIIndexInfoDump(ia); -- Construct the statement. stmt := ' DELETE FROM '|| ia.IndexSchema || '.' || ia.IndexName || '_pidx' || ' WHERE r=:rr'; dbms_output.put_line('ODCIIndexDelete>>>>>'||stmt); -- Parse and execute the statement. cid := dbms_sql.open_cursor; dbms_sql.parse(cid, stmt, dbms_sql.native); dbms_sql.bind_variable_rowid(cid, ':rr', rid); nrows := dbms_sql.execute(cid); dbms_sql.close_cursor(cid); RETURN ODCICONST.SUCCESS; END ODCIIndexDelete;
The ODCIIndexUpdate function is called when a record is updated in a table that contains columns or object attributes indexed by the indextype. The old and new values in the indexed columns are passed in as arguments along with the row identifier.
STATIC FUNCTION ODCIIndexUpdate(ia sys.ODCIIndexInfo, rid VARCHAR2, oldval PowerDemand_Typ, newval PowerDemand_Typ, env sys.ODCIEnv) RETURN NUMBER AS cid INTEGER; cid2 INTEGER; stmt VARCHAR2(1000); stmt2 VARCHAR2(1000); nrows INTEGER; i NUMBER; BEGIN dbms_output.put_line(' '); dbms_output.put_line('ODCIIndexUpdate>>>>> Old'|| ' TotGridDemand= '||oldval.TotGridDemand || ' MaxCellDemand= '||oldval.MaxCellDemand || ' MinCellDemand= '||oldval.MinCellDemand) ; dbms_output.put_line('ODCIIndexUpdate>>>>> New'|| ' TotGridDemand= '||newval.TotGridDemand || ' MaxCellDemand= '||newval.MaxCellDemand || ' MinCellDemand= '||newval.MinCellDemand) ; sys.ODCIIndexInfoDump(ia); -- Delete old entries. stmt := ' DELETE FROM '|| ia.IndexSchema || '.' || ia.IndexName || '_pidx' || ' WHERE r=:rr'; dbms_output.put_line('ODCIIndexUpdate>>>>>'||stmt); -- Parse and execute the statement. cid := dbms_sql.open_cursor; dbms_sql.parse(cid, stmt, dbms_sql.native); dbms_sql.bind_variable_rowid(cid, ':rr', rid); nrows := dbms_sql.execute(cid); dbms_sql.close_cursor(cid); -- Insert new entries. stmt2 := ' INSERT INTO '|| ia.IndexSchema || '.' || ia.IndexName || '_pidx' || ' VALUES (:rr, :pos, :val)'; dbms_output.put_line('ODCIIndexUpdate>>>>>'||stmt2); -- Parse and execute the statement. cid2 := dbms_sql.open_cursor; dbms_sql.parse(cid2, stmt2, dbms_sql.native); dbms_sql.bind_variable_rowid(cid2, ':rr', rid); -- Iterate over the rows of the Varray and insert them. i := newval.CellDemandValues.FIRST; WHILE i IS NOT NULL LOOP -- Bind the row into the cursor for insert. dbms_sql.bind_variable(cid2, ':pos', i); dbms_sql.bind_variable(cid2, ':val', newval.CellDemandValues(i)); nrows := dbms_sql.execute(cid2); dbms_output.put_line('ODCIIndexUpdate>>>>>('|| 'RID' || ' , '|| i || ' , '|| newval.CellDemandValues(i)|| ')'); i := newval.CellDemandValues.NEXT(i); END LOOP; dbms_sql.close_cursor(cid2); RETURN ODCICONST.SUCCESS; END ODCIIndexUpdate;
ODCIIndexUpdate is the last method defined in the CREATE TYPE BODY statement, which ends as follows:
END; /
The optional ODCIIndexGetMetadata function, if present, is called by the Export utility in order to write implementation-specific metadata (which is not stored in the system catalogs) into the export dump file. This metadata might be policy information, version information, user settings, and so on. This metadata is written to the dump file as anonymous PL/SQL blocks that are executed at import time, immediately before the associated index is created.
This method returns strings to the Export utility that comprise the code of the PL/SQL blocks. The Export utility repeatedly calls this method until a zero-length string is returned, thus allowing the creation of any number of PL/SQL blocks of arbitrary complexity. Normally, this method calls functions within a PL/SQL package in order to make use of package-level variables, such as cursors and iteration counters, that maintain state across multiple calls by Export.
For information about the Export and Import utilities, see the Oracle9i Database Utilities manual.
In the power demand cartridge, the only metadata that is passed is a version string of V1.0, identifying the current format of the index-organized table that underlies the domain index. The power_pkg.getversion function generates a call to the power_pkg.checkversion procedure, to be executed at import time to check that the version string is V1.0.
STATIC FUNCTION ODCIIndexGetMetadata(ia sys.ODCIIndexInfo, expversion VARCHAR2, newblock OUT PLS_INTEGER, env sys.ODCIEnv) RETURN VARCHAR2 IS BEGIN -- Let getversion do all the work since it has to maintain state across calls. RETURN power_pkg.getversion (ia.IndexSchema, ia.IndexName, newblock); EXCEPTION WHEN OTHERS THEN RAISE; END ODCIIndexGetMetaData;
The power_pkg package is defined as follows:
CREATE OR REPLACE PACKAGE power_pkg AS FUNCTION getversion(idxschema IN VARCHAR2, idxname IN VARCHAR2, newblock OUT PLS_INTEGER) RETURN VARCHAR2; PROCEDURE checkversion (version IN VARCHAR2); END power_pkg; / SHOW ERRORS; CREATE OR REPLACE PACKAGE BODY power_pkg AS -- iterate is a package-level variable used to maintain state across calls -- by Export in this session. iterate NUMBER := 0; FUNCTION getversion(idxschema IN VARCHAR2, idxname IN VARCHAR2, newblock OUT PLS_INTEGER) RETURN VARCHAR2 IS BEGIN -- We are generating only one PL/SQL block consisting of one line of code. newblock := 1; IF iterate = 0 THEN -- Increment iterate so we'll know we're done next time we're called. iterate := iterate + 1; -- Return a string that calls checkversion with a version 'V1.0' -- Note that export adds the surrounding BEGIN/END pair to form the anon. -- block... we don't have to. RETURN 'power_pkg.checkversion(''V1.0'');'; ELSE -- reset iterate for next index iterate := 0; -- Return a 0-length string; we won't be called again for this index. RETURN ''; END IF; END getversion; PROCEDURE checkversion (version IN VARCHAR2) IS wrong_version EXCEPTION; BEGIN IF version != 'V1.0' THEN RAISE wrong_version; END IF; END checkversion; END power_pkg;
The power demand cartridge creates the indextype for the domain index. The specification includes the list of operators supported by the indextype. It also identifies the implementation type containing the OCDI index routines.
CREATE OR REPLACE INDEXTYPE power_idxtype FOR Power_Equals(PowerDemand_Typ, NUMBER, NUMBER), Power_GreaterThan(PowerDemand_Typ, NUMBER, NUMBER), Power_LessThan(PowerDemand_Typ, NUMBER, NUMBER), Power_EqualsAny(PowerDemand_Typ, NUMBER), Power_GreaterThanAny(PowerDemand_Typ, NUMBER), Power_LessThanAny(PowerDemand_Typ, NUMBER) USING power_idxtype_im;
This section explains the parts of the power demand cartridge as they relate to extensible optimization. Explanatory text and code segments are mixed.
The table PowerCartUserStats is used to store statistics about the hourly power grid readings. These statistics will be used by the method ODCIStatsSelectivity (described later) to estimate the selectivity of operator predicates. Because of the types of statistics collected, it is more convenient to use a separate table instead of letting Oracle store the statistics.
The PowerCartUserStats table contains the following columns:
CREATE TABLE PowerCartUserStats ( -- Table for which statistics are collected tab VARCHAR2(30), -- Column for which statistics are collected col VARCHAR2(30), -- Cell position cpos NUMBER, -- Minimum power demand for the given cell lo NUMBER, -- Maximum power demand for the given cell hi NUMBER, -- Number of (non-null) power demands for the given cell nrows NUMBER ); /
The power demand cartridge creates an object type that specifies methods that will be used by the extensible optimizer. These methods are part of the ODCIStats (Oracle Data Cartridge Interface STATisticS) interface and they collectively define the methods that are called when an ANALYZE command is issued or when the optimizer is deciding on the best execution plan for a query.
Table 13-5 shows the method functions created for the power demand cartridge. (Names of all but one of the functions begin with the string ODCIStats.)
The following statement creates the power_statistics object type. This object type's ODCI methods are used to collect and delete statistics about columns and indexes, compute selectivities of predicates with operators or functions, and to compute costs of domain indexes and functions. The curnum attribute is a dummy attribute that is not used.
CREATE OR REPLACE TYPE power_statistics AS OBJECT ( curnum NUMBER, STATIC FUNCTION ODCIGetInterfaces(ifclist OUT sys.ODCIObjectList) RETURN NUMBER, STATIC FUNCTION ODCIStatsCollect(col sys.ODCIColInfo, options sys.ODCIStatsOptions, rawstats OUT RAW, env sys.ODCIEnv) RETURN NUMBER, STATIC FUNCTION ODCIStatsDelete(col sys.ODCIColInfo, env sys.ODCIEnv) RETURN NUMBER, STATIC FUNCTION ODCIStatsCollect(ia sys.ODCIIndexInfo, options sys.ODCIStatsOptions, rawstats OUT RAW, env sys.ODCIEnv) RETURN NUMBER, STATIC FUNCTION ODCIStatsDelete(ia sys.ODCIIndexInfo, env sys.ODCIEnv) RETURN NUMBER, STATIC FUNCTION ODCIStatsSelectivity(pred sys.ODCIPredInfo, sel OUT NUMBER, args sys.ODCIArgDescList, strt NUMBER, stop NUMBER, object PowerDemand_Typ, cell NUMBER, value NUMBER, env sys.ODCIEnv) RETURN NUMBER, PRAGMA restrict_references(ODCIStatsSelectivity, WNDS, WNPS), STATIC FUNCTION ODCIStatsSelectivity(pred sys.ODCIPredInfo, sel OUT NUMBER, args sys.ODCIArgDescList, strt NUMBER, stop NUMBER, object PowerDemand_Typ, value NUMBER, env sys.ODCIEnv) RETURN NUMBER, PRAGMA restrict_references(ODCIStatsSelectivity, WNDS, WNPS), STATIC FUNCTION ODCIStatsIndexCost(ia sys.ODCIIndexInfo, sel NUMBER, cost OUT sys.ODCICost, qi sys.ODCIQueryInfo, pred sys.ODCIPredInfo, args sys.ODCIArgDescList, strt NUMBER, stop NUMBER, cmppos NUMBER, cmpval NUMBER, env sys.ODCIEnv) RETURN NUMBER, PRAGMA restrict_references(ODCIStatsIndexCost, WNDS, WNPS), STATIC FUNCTION ODCIStatsIndexCost(ia sys.ODCIIndexInfo, sel NUMBER, cost OUT sys.ODCICost, qi sys.ODCIQueryInfo, pred sys.ODCIPredInfo, args sys.ODCIArgDescList, strt NUMBER, stop NUMBER, cmpval NUMBER, env sys.ODCIEnv) RETURN NUMBER, PRAGMA restrict_references(ODCIStatsIndexCost, WNDS, WNPS), STATIC FUNCTION ODCIStatsFunctionCost(func sys.ODCIFuncInfo, cost OUT sys.ODCICost, args sys.ODCIArgDescList, object PowerDemand_Typ, cell NUMBER, value NUMBER, env sys.ODCIEnv) RETURN NUMBER, PRAGMA restrict_references(ODCIStatsFunctionCost, WNDS, WNPS), STATIC FUNCTION ODCIStatsFunctionCost(func sys.ODCIFuncInfo, cost OUT sys.ODCICost, args sys.ODCIArgDescList, object PowerDemand_Typ, value NUMBER, env sys.ODCIEnv) RETURN NUMBER, PRAGMA restrict_references(ODCIStatsFunctionCost, WNDS, WNPS) ); /
The CREATE TYPE statement is followed by a CREATE TYPE BODY statement that specifies the implementation for each member function:
CREATE OR REPLACE TYPE BODY power_statistics IS ...
Each member function is described in a separate section, but the function definitions have the following general form:
STATIC FUNCTION function-name (...) RETURN NUMBER IS END;
The ODCIGetInterfaces function returns the list of names of the interfaces implemented by the type. There is only one set of the extensible optimizer interface routines,