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4 thoughts on “Oracle Indexes and types of indexes in oracle with example”
On both not null columns the size of an index on a varchar2 20 was 2,5 times the size from a varchar2 ! Am I right that apart from the number of indexed table rows the number of tokens is the most important parameter with regard to the space of a context domain index?
If no , what are some other important parameters influencing the size. Thanks in advance for another valuable answer of you. Merge statement in domain index table ver 9i. September 28, - Hi Tom, I want to merge the rows in a table with domain index. Since merge feature is not supported with domain index table what is the alternative other than just delete and insert. I am having it on a partitioned table and I want to local partition the text index and place them on the relevant tablespace.
My Oracle version is Oracle text objects are created on the same tablespace of the table it self in my case its the default tablespace for the user data for that schema. Please disregard the previous issue, I managed to figure it out. Sorry for the inconvenience. Please let me know if you know any information on this issue. I am using oracle Domain indexes causing errors with datapump export March 18, - 1: A datapump export of domain indexes causes error.
This has started after applying CPUJan to Support says they don't know what causes it but it has been fixed in Is there a way of knowing if it has really been fixed since I do not have Invalid indextype version specified ORA Source Code July 01, - 8: Hi Tom, I need one help from your side,I want to select the domain index section group source code.
How can I get that. When physical rowids are fetched from the index table, you can be sure that their length is 18 characters. Universal rowids, however, may be up to characters long, and so a string length function must be used to correctly determine the actual length of a fetched universal rowid.
All values of a primary key column must be unique, so a domain index defined upon a non-unique column of a table cannot use this column as the primary key of an underlying IOT used to store the index. To work around this, you can add a column in the IOT, holding the index data, to hold a unique sequence number.
Whenever a column value is inserted in the table, you should generate a unique sequence number to go with it. The indexed column together with the sequence number can be used as the primary key of the IOT.
This approach also preserves the fast access to primary key column values that is a major benefit of IOTs. To provide similar support for domain indexes, indextype designers can add any domain-specific metadata in the following manner:. Like B-tree and bitmap indexes, domain indexes are exported and subsequently imported when their base tables are exported.
However, domain indexes can have implementation-specific metadata associated with them that are not stored in the system catalogs. For example, a text domain index can have associated policy information, a list of irrelevant words, and so on.
To move the domain index metadata, the indextype needs to implement the ODCIIndexGetMetadata interface routine see the reference chapters for details.
This interface routine gets invoked when a domain index is being exported. The domain index information is passed in as a parameter. It is needed only if the domain index has extra metadata to be moved. The transportable tablespaces feature enables you to move tablespaces from one Oracle database into another. You can use transportable tablespaces to move domain index data as an alternative to exporting and importing it. Also, you do not need to rebuild the index afterward as you do when loading or importing.
Oracle9i Database Administrator's Guide for information about using transportable tablespaces. A user-defined operator is a top-level schema object. It is identified by a name which is in the same namespace as tables, views, types and standalone functions. An operator binding associates an operator with the signature of a function that implements the operator.
A signature consists of a list of the datatypes of the arguments of the function, in order of occurrence, and the function's return type. Binding an operator to a certain signature enables Oracle to pick out the function to execute when the operator is invoked. An operator can be implemented by more than one function as long as each function has a different signature. For each such function, you must define a corresponding binding. Thus, any operator has an associated set of one or more bindings.
Each binding can be evaluated using a user-defined function of any of these kinds:. An operator created in a schema can be evaluated using functions defined in the same or different schemas. The operator bindings can be specified at the time of creating the operator.
It is ensured that the signatures of the bindings are unique. For example, an operator Contains can be created in the Ordsys schema with two bindings and the corresponding functions that provide the implementation in the Text and Spatial domains.
Although the return data type is specified as part of operator binding declaration, it is not considered to determine the uniqueness of the binding, However, the specified function must have the same argument and return datatypes as the operator binding. Namely, if there are any dependent indextypes for any of the operator bindings, then the DROP operation is disallowed.
User-defined operators can be invoked anywhere built-in operators can be used, that is, wherever expressions can occur. For example, user-defined operators can be used in the following:.
When an operator is invoked, the evaluation of the operator is accomplished by executing a function bound to it. The function is selected based on the datatypes of the arguments to the operator. If no function bound to the operator matches the signature with which the operator is invoked perhaps after some implicit type conversions , an error is raised.
Consider the operator Contains being used in the following SQL statements:. The invocation of the operator Contains resume, 'Oracle' is transformed into the execution of the function text.
Similarly, the invocation of the operator Contains location ,: The following statement would raise an error since none of the operator bindings satisfy the argument datatypes:.
An operator can be optionally supported by one or more user-defined indextypes. An indextype can support one or more operators. This means that a domain index of this indextype can be used in efficiently evaluating these operators.
Operators can also be bound to regular functions. For example, an operator Equal can be bound to a function eq number, number that compares two numbers. The DDL for this would be:. Thus, an indextype designer should first design the set of operators to be supported by the indextype. For each of these operators, a functional implementation should be provided. The list of operators supported by an indextype are specified when the indextype schema object is created as described previously.
Both kinds of cases are considered in the following sections. Operators appearing in the WHERE clause can be evaluated efficiently by performing an index scan using the scan methods provided as part of the implementation of an indextype. This involves recognizing operator predicates of a certain form, selection of a domain index, setting up an appropriate index scan, and finally, executing index scan methods.
Let's consider each one of these steps in detail. An indextype supports efficient evaluation of operator predicates that can be represented by a range of lower and upper bounds on the operator return values. Specifically, predicates of the form:. They are evaluated using the functional implementation.
Finally, any other operator predicates which can internally be converted into one of the preceding forms by Oracle can also make use of the index scan based evaluation. An index scan-based evaluation of an operator is a possible candidate for predicate evaluation only if the operator occurring in the predicate as described in the preceding section operates on a column or object attribute indexed using an indextype.
The final decision to choose between the indexed implementation and the functional implementation is made by the optimizer. The optimizer takes into account the selectivity and cost while generating the query execution plan. The optimizer can choose to use a domain index in evaluating the Contains operator if.
If any of these conditions do not hold, a complete scan of the Employees table is performed and the functional implementation of Contains is applied as a post-filter. If these conditions are met, the optimizer uses selectivity and cost functions to compare the cost of index-based evaluation with the full table scan and appropriately generates the execution plan.
In this query, the Employees table could be accessed through an index on the id column or one on the resume column. The optimizer estimates the costs of the two plans and picks the cheaper one, which could be to use the index on id and apply the Contains operator on the resulting rows. In this case, the functional implementation of Contains is used and the domain index is not used. If a domain index is selected for the evaluation of an operator predicate, an index scan is set-up.
The ODCIIndexStart method is invoked with the operator related information including name and arguments and the lower and upper bounds describing the predicate. The index scan routines must be implemented with an understanding of how the routines' invocations are ordered and how multiple sets of invocations can be interleaved.
If the optimizer decides to use the domain indexes on the resume columns of both tables, the indextype routines may be invoked in the following sequence:. Thus, the same indextype routine may be invoked but for different instances of operators.
At any time, many operators are being evaluated through the same indextype routines. In case of a routine that does not need to maintain any state across calls because all the information is obtained through its parameters as with the create routine , this is not a problem.
However, in case of routines needing to maintain state across calls like the fetch routine, which needs to know which row to return next , the state should be maintained in the SELF parameter that is passed in to each call. The SELF parameter which is an instance of the implementation type can be used to store either the entire state if it is not too big or a handle to the cursor-duration memory that stores the state. Operators occurring in expressions other than in the WHERE clause are evaluated using the functional implementation.
The function is invoked by passing it the actual value of the resume text data in the current row. Note that this function would not make use of any domain indexes that may have been built on the resume column.
However, it is possible to have a functional implementation for an operator that makes use of a domain index. The following sections discuss how functions that use domain indexes can be written and how they are invoked by the system. For many domain-specific operators, such as Contains , the functional implementation can work in two ways:.
For example, when Contains resume , 'Oracle' is invoked on a particular row of the Employee table, it is easier for the function to look up the text domain index defined on the resume column and evaluate the operator based on the row identifier for the row containing the resume - rather than work on the resume text data argument.
To achieve both the behaviors of 1 and 2 , the functional implementation is provided using a regular function which has three additional arguments--that is, additional to the original arguments to the operator.
The additional arguments are:. For example, the index-based functional implementation for the Contains operator is provided by the following function. The Contains operator is bound to the functional implementation as follows:. It must be the same as the implementation type of the relevant indextype that supports this operator. Oracle invokes the functional implementation for the operator if the operator appears outside the WHERE clause.
If the functional implementation is index-based that is, defined to use an indextype , the additional index information is passed in as arguments only if the operator's first argument is a column or object attribute with a domain index of the appropriate indextype defined on it. When index information is passed in, the implementation can compute the operator value by doing a domain index lookup using the row identifier as key.
The index metadata is used to identify the index structures associated with the domain index. The scan context is typically used to share state with the subsequent invocations of the same operator. Apart from filtering rows, an operator occurring in the WHERE clause might need to support returning ancillary data.
Ancillary data is modeled as an operator or multiple operators with a single literal number argument. It has a functional implementation that has access to state generated by the index scan-based implementation of the primary operator occurring in the WHERE clause. Contains is the primary operator and can be evaluated using an index scan which, in addition to determining the rows that satisfy the predicate, also computes a score value for each row.
The functional implementation for the Score operator simply accesses the state generated by the index scan to obtain the score for a given row identified by its row identifier. The literal argument 1 associates the ancillary operator Score to the corresponding primary operator Contains which generates the ancillary data. In summary, ancillary data is modeled as independent operator s and is invoked by the user with a single number argument that ties it with the corresponding primary operator.
Its functional implementation makes use of either the domain index or the state generated by the primary operator occurring in the WHERE clause. The functional implementation is invoked with extra arguments: The following sections discuss how operators modeling ancillary data are defined and invoked.
An indextype designer needs to specify that an operator binding computes ancillary data. Such a binding is referred to as a primary binding. For example, a primary binding for Contains can be defined as follows:. An indextype designer has to implement the functional implementation for ancillary data operators in a manner similar to the index-based functional implementation.
As discussed earlier, the function takes extra arguments. After the function is defined, the indextype designer can bind it to the operator with an additional ANCILLARY TO attribute, which indicates that the functional implementation needs to share state with the primary operator binding. The binding that is used for modeling ancillary data is referred to as the ancillary operator binding. For example, let the TextScore function contain code to evaluate the Score ancillary operator.
The operators corresponding to ancillary data are invoked by the user with a single number argument. The number argument must be a literal in both the ancillary operation and the primary operator invocation. This is required so that the operator association can be done at the query compilation time.
The corresponding primary operator invocation in the query is determined by matching it with the number passed in as the last argument to the primary operator. After the matching primary operator invocation is found it is an error to find zero or more than one matching primary operator invocation:. The invocation of Score is determined to be ancillary to Contains based on the number argument 1 , and the functional implementation for Score gets the following operands: The execution involves using an index scan to process the Contains operator.
For each of the rows returned by the fetch call of the index scan, the functional implementation of Score is invoked by passing it the ODCIIndexCtx argument, which contains the index information, row identifier, and a handle to the index scan state.
The functional implementation can use the handle to the index scan state to compute the score. Thus, the order in which these objects must be created, or their definitions exported for future Import are:.
The following table shows the default and explicit drop options supported for operators and indextypes. The other schema objects are included for completeness and the corresponding drop behavior already available in Oracle. Invalid objects are automatically revalidated, if possible, the next time they are referenced.
A domain index can be built to have discrete index partitions that correspond to the partitions of a range-partitioned table. Such an index is called a local domain index , as opposed to a global domain index, which has no index partitions. The term local domain index refers to a partitioned index as a whole, not to the partitions that comprise a local domain index. A local domain index is equipartitioned with the underlying table: Currently, local domain indexes can be created only for range-partitioned tables.
Local domain indexes cannot be built for hash-partitioned tables or IOTs. A local as opposed to a global domain index can index only a single column; it cannot index an expression.
Here is the syntax:. Use this syntax to create a local domain index. You can specify partition names or allow Oracle to generate them. The maximum length of the parameter string is characters. When you specify this clause at the top level of the syntax, the parameters become the default parameters for the index partitions. A specified index partition cannot be dropped explicitly.
To drop a local index partition, the entire local domain index must be dropped:. Like a domain index, a partition of a local domain index can be in one or more of several states:. The state is generally transitional and temporary. Same as for regular indexes: This property is associated only with an index, never with an index partition.
The database itself will figure out to use the index. So you should just do the same select as in your first example. Alternatively, if you want to know if the server will use a plan using your newly created index, you can inspect the output of the explain command:.