This chapter describes the functions and procedures that comprise the interface to the extensible optimizer.
This chapter contains these topics:
This section discusses the components of the Extensible Optimizer interface.
The extensible optimizer interfaces support working with partitioned tables and domain indexes. This is accomplished in two ways:
Additional attributes have been added to some systemdefined object types that are parameters to the ODCIStats
interface methods. For example, the ODCIColInfo
type is enhanced to add information about the column's partition.
Arguments or semantics of the arguments have changed for some ODCIStats
methods.
Note that you must update your code for ODCIStats2
version of the ODCIStats
interfaces to use your statistics type with an indextype that implements the ODCIIndex2
version of the extensible indexing interfaces.
Example 211 Using Statistics Functions in an Extensible Optimizer Interface
Consider an example of how the statistics functions might be used. Suppose, in the schema HR
, we define the following:
CREATE OPERATOR Contains binding (VARCHAR2(4000), VARCHAR2(30)) RETURN NUMBER USING Contains_fn; CREATE TYPE stat1 ( ..., STATIC FUNCTION ODCIStatsSelectivity(pred ODCIPredInfo, sel OUT NUMBER, args ODCIArgDescList, start NUMBER, stop NUMBER, doc VARCHAR2(4000), key VARCHAR2(30)) return NUMBER, STACTIC FUNCTION ODCIStatsFunctionCost(func ODCIFuncInfo, cost OUT ODCICost, args ODCIArgDescList, doc VARCHAR2(4000), key VARCHAR2(30)) return NUMBER, STATIC FUNCTION ODCIStatsIndexCost(ia ODCIIndexInfo, sel NUMBER, cost OUT ODCICost, qi ODCIQueryInfo, pred ODCIPredInfo, args ODCIArgDescList, start NUMBER, stop NUMBER, key VARCHAR2(30)) return NUMBER, ... ); CREATE TABLE T (resume VARCHAR2(4000)); CREATE INDEX T_resume on T(resume) INDEXTYPE IS indtype; ASSOCIATE STATISTICS WITH FUNCTIONS Contains_fn USING stat1; ASSOCIATE STATISTICS WITH INDEXTYPE indtype USING stat1 WITH SYSTEM MANAGED STORAGE TABLES;
When the optimizer encounters the query
SELECT * FROM T WHERE Contains(resume, 'ORACLE') = 1,
it computes the selectivity of the predicate by invoking the userdefined selectivity function for the functional implementation of the Contains
operator. In this case, the selectivity function is stat1.ODCIStatsSelectivity
. It is called as follows:
stat1.ODCIStatsSelectivity ( ODCIPredInfo('HR', 'Contains_fn', NULL, 29), sel, ODCIArgDescList( ODCIArgDesc(ODCIConst.ArgLit, NULL, NULL, NULL, NULL, NULL, NULL), ODCIArgDesc(ODCIConst.ArgLit, NULL, NULL, NULL, NULL, NULL, NULL), ODCIArgDesc(ODCIConst.ArgCol, 'T', 'HR', '"RESUME"', NULL, NULL, NULL), ODCIArgDesc(ODCIConst.ArgLit, NULL, NULL, NULL, NULL, NULL, NULL)), 1, 1, NULL, 'ORACLE')
Suppose the selectivity function returns a selectivity of 3 (percent). When the domain index is being evaluated, then the optimizer calls the userdefined index cost function as follows:
stat1.ODCIStatsIndexCost ( ODCIIndexInfo('HR', 'T_RESUME', ODCIColInfoList(ODCIColInfo('HR', 'T', '"RESUME"', NULL, NULL, NULL, 0, 0, 0, 0)), NULL, 0, 0, 0, 0), 3, cost, NULL, ODCIPredInfo('HR', 'Contains', NULL, 13), ODCIArgDescList( ODCIArgDesc(ODCIConst.ArgLit, NULL, NULL, NULL, NULL, NULL, NULL), ODCIArgDesc(ODCIConst.ArgLit, NULL, NULL, NULL, NULL, NULL, NULL), ODCIArgDesc(ODCIConst.ArgLit, NULL, NULL, NULL, NULL, NULL, NULL)), 1, 1, 'ORACLE')
Suppose that the optimizer decides not to use the domain index because it is too expensive. Then it calls the userdefined cost function for the functional implementation of the operator as follows:
stat1.ODCIStatsFunctionCost ( ODCIFuncInfo('HR', 'Contains_fn', NULL, 1), cost, ODCIArgDescList( ODCIArgDesc(ODCIConst.ArgCol, 'T', 'HR', '"RESUME"', NULL, NULL, NULL), ODCIArgDesc(ODCIConst.ArgLit, NULL, NULL, NULL, NULL, NULL, NULL)), NULL, 'ORACLE')
The following sections describe each statistics type function in greater detail.
EXPLAIN
PLAN
shows the userdefined CPU and I/O costs for domain indexes in the CPU_COST
and IO_COST
columns of PLAN_TABLE
. For example, suppose we have a table Emp_tab
and a userdefined operator Contains
. Further, suppose that there is a domain index EmpResume_indx
on the Resume_col
column of Emp_tab
, and that the indextype of EmpResume_indx
supports the operator Contains
. Then, the query
SELECT * FROM Emp_tab WHERE Contains(Resume_col, 'Oracle') = 1
might have the following plan:
OPERATION  OPTIONS  OBJECT_NAME  CPU_COST  IO_COST 

SELECT STATEMENT 

TABLE ACCESS 
BY ROWID 
EMP_TAB 

DOMAIN INDEX 
EMPRESUME_INDX 
300 
4 
The index hint applies to domain indexes. In other words, the index hint forces the optimizer to use the hinted index for a userdefined operator, if possible.
The hint ORDERED_PREDICATES
forces the optimizer to preserve the order of predicate evaluation (except predicates used for index keys) as specified in the WHERE
clause of a SQL DML statement.
Userdefined ODCIStats
functions are used for table columns, functions, package, type, indextype or domain indexes. These functions are described in the following sections.
Table 211 Summary of UserDefined ODCIStats Functions
Function  Description 

Discover which version of the 

Called by the 

Deletes userdefined statistics on a table, a partition of a table, an index, or a partition of an index. 

Computes the cost of a function. 

Exchanges domain index statistics when an 

Calculates the cost of a domain index scan. 

Specifies the selectivity of a predicate. 

Provides cardinality statistics for table functions and input cursor expressions. 

Updates statistics during partition maintenance operations. Patches the domain index statistics. 
ODCIGetInterfaces
is invoked by the server to discover which version of the ODCIStats
interface the user has implemented in the methods of the userdefined statistics type.
FUNCTION ODCIGetInterfaces( ifclist OUT ODCIObjectList) RETURN NUMBER;
Parameter  IN/OUT  Description 

ifclist 
OUT 
The version of the ODCIStats interfaces implemented by the statistics type. This value should be SYS.ODCISTATS2 . 
ODCIConst.Success
on success, ODCIConst.Error
otherwise.
Called by the DBMS_STATS
package to collect userdefined statistics.
Syntax  Description 

FUNCTION ODCIStatsCollect( col ODCIColInfo, options ODCIStatsOptions, statistics OUT RAW, env ODCIEnv) return NUMBER; 
Called by the DBMS_STATS package to collect userdefined statistics on a table or a partition of a table. 
FUNCTION ODCIStatsCollect( ia ODCIIndexInfo, options ODCIStatsOptions, statistics OUT RAW, env ODCIEnv) return NUMBER; 
Called to collect userdefined statistics on an index or a partition of an index. 
Parameter  IN/OUT  Description 

col 

Column for which statistics are being collected 
options 

Options passed to DBMS_STATS 
statistics 

Userdefined statistics collected 
env 

Contains general information about the environment in which the routine is executing 
ia 

Domain index for which statistics are being collected 
The function returns ODCIConst.Success
, ODCIConst.Error
, or ODCIConst.Warning.
This function should be implemented as a STATIC
type method.
If statistics are being collected for only one partition, the TablePartition
field in the ODCIColInfo
type is filled in with the name of the partition. Otherwise (if statistics must be collected for all the partitions or for the entire table), the TablePartition
field is null.
If the DBMS_STATS
package methods are executed to collect userdefined statistics on a partitioned table, then n+1
ODCIStatsCollect
calls are made, where n
is the number of partitions in the table. The first n
calls are made with the TablePartition
attribute in ODCIColInfo
filled in with the partition name and the ODCIStatsOptions.CallProperty
set to IntermediateCall
. The last call is made with ODCIEnv.CallPropertyflag
set to FinalCall
to allow you to collect aggregate statistics for the entire table.
If userdefined statistics are being collected for only one partition of the table, two ODCIStatsCollect
calls are made. In the first, you should collect statistics for the partition. For this call, the TablePartition
attribute of the ODCIColInfo
structure is filled in and the ODCIEnv.CallProperty
is set to FirstCall
.
In the second call you can update the aggregate statistics of the table based upon the new statistics collected for the partition. In this call, the ODCIEnv.CallPropertyflag
is set to FinalCall
to indicate that it is the second call. The ODCIColInfo.TablePartition
is filled in with the partition name in both the calls.
The ODCIStatsCollect() method is invoked only one time for a nonpartitioned domain index, a partitioned domain index and a partition in a domain index. If the statistics are being collected only for one partition in a domain index, the IndexPartitionNum
field in the ODCIIndexInfo
type is filled in with the partition number. Otherwise, the IndexPartitionNum
field is null
.
Because the statistics OUT RAW
argument of statistics is not used in the new interface, the cartridge developer should store the userdefined statistics result in some userdefined tables.
If a nonpartitioned domain index is being ANALYZE
d, the user should collect statistics for the domain index.
If a partitioned domain index is being ANALYZE
d,
ODCIEnv.CallProperty = StatsGlobalAndPartition
means that the user should collect statistics for all partitions in the domain index and then aggregate statistics of the domain index based upon the statistics collected for all the partitions
ODCIEnv.CallProperty = StatsGlobal
means that the user should aggregate domain index statistics from the statistics of all the domain index partitions.
ODCIEnv.CallProperty = StatsPartition
means that the user should collect statistics for all index partitions in the domain index.
If only one partition of the domain index is being ANALYZE
d,
ODCIEnv.CallProperty = StatsGlobalAndPartition
means that the user should collect statistics for the single index partition and then aggregate statistics of the domain index based upon the statistics of all the partitions.
ODCIEnv.CallProperty = StatsGlobal
means that the user should aggregate domain index statistics from the statistics of all the index partitions.
ODCIEnv.CallProperty = StatsPartition
means that the user should collect statistics for the single index partition.
Note that when ODCIEnv.CallProperty = StatsGlobalAndPartition
or StatsGlobal
, the user should aggregate statistics for the domain index, depending on the availability of the statistics collected for the other index partitions. If the statistics for all the index partitions are available, aggregate these statistics. If any one statistics for an index partition is absent, do nothing.
ODCIStatsDelete
is called to delete userdefined statistics.
Syntax  Description 

FUNCTION ODCIStatsDelete( col ODCIColInfo, statistics OUT RAW, env ODCIEnv) return NUMBER; 
Deletes userdefined statistics on a table or a partition of a table. 
FUNCTION ODCIStatsDelete( ia ODCIIndexInfo, statistics OUT RAW, env ODCIEnv) return NUMBER; 
Deletes userdefined statistics on an index or a partition of an index. 
Parameter  IN/OUT  Description 

col 

Column for which statistics are being deleted 
statistics 
OUT 
Contains tablelevel aggregate statistics for a partitioned table or index 
env 

Contains general information about the environment in which the routine is executing 
ia 

Domain index for which statistics are deleted 
ODCIConst.Success
, ODCIConst.Error
, or ODCIConst.Warning.
This function should be implemented as a STATIC
method.
When the function is called for a nonpartitioned table, the statistics
argument in the ODCIStatsDelete
interface is ignored.
If the statistics are being deleted for a partitioned table, the ODCIStatsDelete
is called n+1
times. The first n
calls are with the partition name filled in the ODCIColInfo
structure and the ODCIEnv.CallProperty
set to IntermediateCall
. The last call is made with the ODCIEnv.CallProperty
set to FinalCall
.
In the first call, delete the statistics for the specific partitions; and in the last call drop or clean up any structures created for holding statistics for the deleted table. The ODCIColInfo.TablePartition
is set to null in the last call. In the first call, the TablePartition
field is filled in.
If statistics are being deleted for only one partition and the _minimal_stats_aggregation
parameter is set to FALSE
, two ODCIStatsDelete
calls are made. In each call, ODCIColInfo.TablePartition
is filled in with the partition name. On the first call, delete any userdefined statistics collected for that partition. On the second call, update the aggregate statistics for the table.
If statistics are being deleted for one partition and _minimal_stats_aggregation
is set to TRUE
, ODCIStatsDelete
is only called one to delete any userdefined statistics collected for that partition.
The initial value of _minimal_stats_aggregation
is TRUE
.
The ODCIStatsDelete() method is invoked only one time for nonpartitioned domain index, partitioned domain index, or an index partition.
If the statistics is being deleted for a nonpartitioned domain index, the user should delete userdefined statistics for the domain index.
If the statistics is being deleted for a partitioned domain index, the user should delete the aggregated statistics of the domain index and optionally delete userdefined statistics for all domain index partitions, depending on Options
in ODCIEnv.CallProperty
:
ODCIEnv.CallProperty = StatsGlobalAndPartition
means that the user should delete statistics for all the domain index partitions and aggregated statistics of the domain index.
ODCIEnv.CallProperty = StatsGlobal
means that the user should delete the aggregated statistics of the domain index.
ODCIEnv.CallProperty = StatsPartition
is not valid option.
If the statistics is being deleted for only one partition of the index, the user should delete userdefined statistics for the index partition.
Computes the cost of a function.
FUNCTION ODCIStatsFunctionCost(
func ODCIFuncInfo,
cost OUT ODCICost,
args ODCIArgDescList,
list,
env ODCIEnv)
return NUMBER;
Parameter  IN/OUT  Description 

func 

Function or type method for which the cost is being computed 
cost 
OUT 
Computed cost (must be positive whole numbers) 
args 

Descriptor of actual arguments with which the function or type method was called. If the function has n arguments, the args array contains n elements, each describing the actual arguments of the function or type method 
list

List of actual parameters to the function or type method; the number, position, and type of each argument must be identical in the function or type method.  
env 

Contains general information about the environment in which the routine is executing 
ODCIConst.Success
, ODCIConst.Error
, or ODCIConst.Warning.
This function should be implemented as a static type method.
Exchanges domain index statistics when an ALTER TABLE EXCHANGE PARTITION ... INCLULDING INDEXES
command is issued.
FUNCTION ODCIStatsExchangePartition( ia ODCIIndexInfo, ia1 ODCIIndexInfo, env ODCIEnv) return NUMBER;
Parameter  IN/OUT  Description 

ia 

Information about the partition that must be exchanged 
sia1 

Information about the index of the nnpartitioned table with which the partition is exchanged 
env 
Contains general information about the environment in which the routine is executing 
ODCIConst.Success
, ODCIConst.Error
, or ODCIConst.Warning
This method should be implemented as a STATIC
type.
This method should be capable of converting the statistics associated with a domain index partition into statistics associated with a nonpartitioned domain index, and the reverse. If the statistics are missing for one of the indexes or index partitions, the user should be able to delete these statistics.
Calculates the cost of a domain index scan, either a scan of the entire index or a scan of one or more index partitions if a local domain index has been built.
FUNCTION ODCIStatsIndexCost( ia ODCIIndexInfo, sel NUMBER, cost OUT ODCICost, qi ODCIQueryInfo, pred ODCIPredInfo, args ODCIArgDescList, start operator_return_type, stop operator_return_type, list, env ODCIEnv) return NUMBER;
Parameter  IN/OUT  Description 

ia 

domain index for which statistics are being collected 
sel 

the usercomputed selectivity of the predicate 
cost 

computed cost (must be positive whole numbers) 
qi 
Information about the query  
pred 
Information about the predicate  
args 
Descriptor of start , stop , and actual value arguments with which the operator was called. If the operator has n arguments, the args array contains n+1 elements, the first element describing the start value, the second element describing the stop value, and the remaining n1 elements describing the actual value arguments of the operator (that is, the arguments after the first) 

start 
Lower bound of the operator (for example, 2 for a predicate fn(...) > 2) 

stop 
Upper bound of the operator (for example, 5 for a predicate fn(...) < 5 ) 

list

List of actual parameters to the operator (excluding the first); the number, position, and type of each argument must be identical to the one in the operator.  
env 
Contains general information about the environment in which the routine is executing 
ODCIConst.Success
, ODCIConst.Error
, or ODCIConst.Warning
For each table in the query, the optimizer uses partition pruning to determine the range of partitions that may be accessed. These partitions are called interesting partitions. The set of interesting partitions for a table is also the set of interesting partitions for all domain indexes on that table. The cost of a domain index can depend on the set of interesting partitions, so the optimizer passes a list of interesting index partitions to ODCIStatsIndexCost
in the args
argument (the type of this argument, ODCIArgDescList
, is a list of ODCIArgDesc
argument descriptor types) for those arguments that are columns. For nonpartitioned domain indexes or for cases where no partition pruning is possible, no partition list is passed to ODCIStatsIndexCost
, and you should assume that the entire index is accessed.
The domain index key can contain multiple column arguments (for example, the indexed column and column arguments from other tables appearing earlier in a join order). For each column appearing in the index key, the args
argument contains the list of interesting partitions for the table. For example, for an index key
op(T1.c1, T2.c2) = 1
the optimizer passes a list of interesting partitions for tables T1
and T2
if they are partitioned and there is partition pruning for them.
This function should be implemented as a static type method.
Only a single call is made to the ODCIStatsIndexCost() function for queries on partitioned or nonpartitioned tables. For queries on partitioned tables, additional information is passed in the ODCIStatsIndexCost() function. Note that some partitions in the list passed to ODCIStatsIndexCost() may not actually be accessed by the query. The list of interesting partitions chiefly serves to exclude partitions that are definitely not accessed.
When the ODCIStatsIndexCost() function is invoked, users can fill in a string in the IndexCostInfo
field of the cost attribute to supply any additional information that might be helpful. The string (255 characters maximum) is displayed in the OPTIONS
column in the EXPLAIN PLAN
output when an execution plan chooses a domain index scan.
Users implementing this function must return 'SYS.ODCISTATS2'
in the ODCIGetInterfaces() call.
Specifies the selectivity of a predicate. The selectivity of a predicate involving columns from a single table is the fraction of rows of that table that satisfy the predicate. For predicates involving columns from multiple tables (for example, join predicates), the selectivity should be computed as a fraction of rows in the Cartesian product of those tables.
FUNCTION ODCIStatsSelectivity( pred ODCIPredInfo, sel OUT NUMBER, args ODCIArgDescList, start function_return_type, stop function_return_type, list, env ODCIEnv) return NUMBER;
Parameter  IN/OUT  Description 

pred 

Predicate for which the selectivity is being computed 
sel 

The computed selectivity, expressed as a number between (and including) 0 and 100, representing a percentage. 
args 

Descriptor of start , stop , and actual arguments with which the function, type method, or operator was called. If the function has n arguments, the args array contains n+2 elements, the first element describing the start value, the second element describing the stop value, and the remaining n elements describing the actual arguments of the function, method, or operator 
start 
Lower bound of the function (for example, 2 for a predicate fn(...) > 2 ) 

stop 
Upper bound of the function (for example, 5 for a predicate fn(...) < 5) 

list 
List of actual parameters to the function or type method; the number, position, and type of each argument must be identical to the one in the function, type method, or operator.  
env 
Contains general information about the environment in which the routine is executing 
ODCIConst.Success
, ODCIConst.Error
, or ODCIConst.Warning
As in ODCIStatsIndexCost
, the args argument contains a list of interesting partitions for the tables whose columns are referenced in the predicate for which the selectivity has to be computed. These interesting partitions are partitions that cannot be eliminated by partition pruning as possible candidates to be accessed. The set of interesting partitions is passed to the function only if partition pruning has occurred (in other words, the interesting partitions are a strict subset of all the partitions).
For example, when ODCIStatsSelectivity
is called to compute the selectivity of the predicate:
f(T1.c1, T2.c2) > 4
the optimizer passes the list of interesting partitions for the table T1
(in the argument descriptor for column T1.c1
) if partition pruning is possible; similarly for the table T2
.
If a predicate contains columns from several tables, this information is indicated by the flag bit PredMultiTable
, set in the Flags
attribute of the pred
argument.
This function should be implemented as a static type method.
Users implementing this interface must return 'SYS.ODCISTATS2'
in the ODCIGetInterfaces
call.
The selectivity of a predicate involving columns from a single table is the fraction of rows of that table that satisfy the predicate. For predicates involving columns from multiple tables (for example, join predicates), the selectivity should be computed as a fraction of rows in the Cartesian product of those tables. For tables with partition pruning, the selectivity should be expressed relative to the cardinalities of the interesting partitions of the tables involved.
The selectivity of predicates involving columns on partitioned tables is computed relative to the rows in the interesting partitions. Thus, the selectivity of the predicate
g(T1.c1) < 5
is the percentage of rows in the set of interesting partitions (or all partitions if no partition pruning is possible) that satisfies this predicate. For predicates with columns from multiple tables, the selectivity must be relative to the number of rows in the cartesian product of the tables.
For example, consider the predicate:
f(T1.c1, T2.c2) > 4
Suppose that the number of rows in the interesting partitions is 1000 for T1
and 5000 for T2
. The selectivity of this predicate must be expressed as the percentage of the 5,000,000 rows in the Cartesian product of T1
and T2
that satisfy the predicate.
If a predicate contains columns from several tables, this information is indicated by the flag bit PredMultiTable
set in the Flags
attribute of the pred
argument.
A selectivity expressed relative to the base cardinalities of the tables involved may be only an approximation of the true selectivity if cardinalities (and other statistics) of the tables have been reduced based on singletable predicates or other joins earlier in the join order. However, this approximation to the true selectivity should be acceptable to most applications.
Only one call is made to the ODCIStatsSelectivity
function for queries on partitioned or nonpartitioned tables. In the case of queries on partitioned tables, additional information is passed while calling the ODCIStatsSelectivity
function.
This function provides cardinality statistics for table functions and input cursor expressions.
STATIC FUNCTION ODCIStatsTableFunction(
func IN SYS.ODCIFuncInfo,
outStats OUT SYS.ODCITabFuncStats,
argDesc IN SYS.ODCIArgDescList,
list)
RETURN NUMBER;
Parameter  IN/OUT  Description 

func 

Table function name 
outStats 

Number of rows expected to be returned 
argDesc 

Description of the arguments to the table function 
list 
The arguments' compiletime values. Expressions that only have values at run time are represented by nulls. 
ODCIConst.Success
, ODCIConst.Error
, or ODCIConst.Warning.
Updates statistics during partition maintenance operations. This lets the statistics type patch up the domain index statistics to correctly reflect the partition maintenance operation.
STATIC FUNCTION ODCIStatsCollect( ia ODCIIndexInfo, palist ODCIPartInfoList, env ODCIEnv) RETURN NUMBER
Parameter  IN/OUT  Description 

ia 

Contains information about the domain index. It does not contain any partition specific information 
palist 

Contains information about the partitions that are to be dropped or added 
env 
Environment handle passed to the routine 
ODCIConst.Success
, ODCIConst.Error
, or ODCIConst.Warning.
When the statistics type is specified by the SYSTEM MANAGED
approach, then the ODCIStatsUpdPartStatistics() method is invoked only one time during PMO. Only DML and query are allowed in the method implementation.
If the user maintains the domain index statistics in a global nonpartitioned table, then the user should delete the entry for the userdefined statistics for the dropped partition (and optionally add a NULL
entry for added partition). They can then check if ODCIEnv.CallProperty
is StatsGlobalAndPartition
or StatsPartition
. If ODCIEnv.CallProperty
is StatsGlobalAndPartition
then they should aggregate all the available index partition statistics. If ODCIEnv.CallProperty
is StatsPartition
they can simply delete the aggregate statistics, or leave the aggregate statistics as they are. ODCIEnv.CallProperty
cannot be StatsGlobal
for this call.
The user should use the information passed in by the ODCIEnv.CallProperty
to determine the type of statistics to delete and adjust.
If the method returns ODCIConst.Error
, the error is ignored and the partition management operation continues.