6
Metadata

This chapter describes how to retrieve metadata about result sets or the database as a whole.

It includes the following topics:

Overview of Metadata

Database objects have various attributes that describe them, and you obtain information about a particular schema object by performing a DESCRIBE operation for the object. The result can be accessed as an object of the Metadata class in that you can use class methods to get the actual values of an object. You accomplish this by passing object attributes as arguments to the various methods of the Metadata class.

You can perform an explicit DESCRIBE operation on the database as a whole, on the types and properties of the columns contained in a ResultSet class or on any of the following schema and subschema objects:

Tables
Views
Procedures
Functions
Packages
Types
Type Attributes
Type Methods
Collections
Synonyms
Sequences
Columns
Argument
Results
Lists

You must specify the type of the attribute you are looking for. By using the getAttributeCount, getAttributeId, and getAttributeType methods of the MetaData class, you can scan through each available attribute.

All DESCRIBE information is cached until the last reference to it is deleted. Users are in this way prevented from accidentally trying to access DESCRIBE information that is already freed.

You obtain metadata by calling the getMetaData method on the Connection class in case of an explicit describe, or by calling the getColumnListMetaData method on the ResultSet class to get the metadata of the result set columns. Both methods return a MetaData object with the described information. The MetaData class provides the getxxx methods to access this information.

Notes on Types and Attributes

When performing DESCRIBE operations, be aware of the following issues:

The ATTR_TYPECODE returns typecodes that represent the type supplied when you created a new type by using the CREATE TYPE statement. These typecodes are of the enumerated type OCCITypeCode, which are represented by OCCI_TYPECODE constants.

Note:
Internal PL/SQL types (boolean, indexed table) are not supported.
The ATTR_DATA_TYPE returns types that represent the datatypes of the database columns. These values are of enumerated type OCCIType. For example, LONG types return OCCI_SQLT_LNG types.

Describing Database Metadata

Describing database metadata is equivalent to an explicit DESCRIBE operation. The object to describe must be an object in the schema. In describing a type, you call the getMetaData method from the connection, passing the name of the object or a RefAny object. To do this, you must initialize the environment in the OBJECT mode. The getMetaData method returns an object of type MetaData. Each type of MetaData object has a list of attributes that are part of the describe tree. The describe tree can then be traversed recursively to point to subtrees containing more information. More information about an object can be obtained by calling the getxxx methods.

If you need to construct a browser that describes the database and its objects recursively, then you can access information regarding the number of attributes for each object in the database (including the database), the attribute ID listing, and the attribute types listing. By using this information, you can recursively traverse the describe tree from the top node (the database) to the columns in the tables, the attributes of a type, the parameters of a procedure or function, and so on.

For example, consider the typical case of describing a table and its contents. You call the getMetaData method from the connection, passing the name of the table to be described. The MetaData object returned contains the table information. Since you are aware of the type of the object that you want to describe (table, column, type, collection, function, procedure, and so on), you can obtain the attribute list as shown in Table 6-1. You can retrieve the value into a variable of the type specified in the table by calling the corresponding get*() method.

Table 6-1 Attribute Groupings

Attribute Type	Description
Parameter Attributes	Attributes belonging to all elements
Table and View Attributes	Attributes belonging to tables and views
Procedure, Function, and Subprogram Attributes	Attributes belonging to procedures, functions, and package subprograms
Package Attributes	Attributes belonging to packages
Type Attributes	Attributes belonging to types
Type Attribute Attributes	Attributes belonging to type attributes
Type Method Attributes	Attributes belonging to type methods
Collection Attributes	Attributes belonging to collection types
Synonym Attributes	Attributes belonging to synonyms
Sequence Attributes	Attributes belonging to sequences
Column Attributes	Attributes belonging to columns of tables or views
Argument and Result Attributes	Attributes belonging to arguments / results
List Attributes	Attributes that designate the list type
Schema Attributes	Attributes specific to schemas
Database Attributes	Attributes specific to databases

Metatdata Code Examples

This section provides code examples for obtaining:

Connection metadata
ResultSet metadata

Connection Metadata Code Examples

The following code example demonstrates how to obtain metadata about attributes of a simple database table:

/* Create an environment and a connection to the HR database */
.
.
.
/* Call the getMetaData method on the Connection object obtainedv*/
MetaData emptab_metaData = connection->getMetaData("EMPLOYEES",
                                                    MetaData::PTYPE_TABLE);
/* Now that you have the metadata information on the EMPLOYEES table,
   call the getxxx methods using the appropriate attributes
*/
/* Call getString */
cout<<"Schema:"<<(emptab_metaData.getString(MetaData::ATTR_OBJ_SCHEMA))<<endl;

if(emptab_metaData.getInt(emptab_metaData::ATTR_PTYPE)==MetaData::PTYPE_TABLE)
    cout<<"EMPLOYEES is a table"<<endl;
else
    cout<<"EMPLOYEES is not a table"<<endl;

/* Call getInt to get the number of columns in the table */
int columnCount=emptab_metaData.getInt(MetaData::ATTR_NUM_COLS);
cout<<"Number of Columns:"<<columnCount<<endl;

/* Call getTimestamp to get the timestamp of the table object */
Timestamp tstamp = emptab_metaData.getTimestamp(MetaData::ATTR_TIMESTAMP);
/* Now that you have the value of the attribute as a Timestamp object,
   you can call methods to obtain the components of the timestamp */
int year;
unsigned int month, day;
tstamp.getData(year, month, day);

/* Call getVector for attributes of list type,
for example ATTR_LIST_COLUMNS
*/
vector<MetaData>listOfColumns;
listOfColumns=emptab_metaData.getVector(MetaData::ATTR_LIST_COLUMNS);

/* Each of the list elements represents a column metadata,
   so now you can access the column attributes
*/
for (int i=0;i<listOfColumns.size();i++
{
   MetaData columnObj=listOfColumns[i];
   cout<<"Column Name:"<<(columnObj.getString(MetaData::ATTR_NAME))<<endl;
   cout<<"Data Type:"<<(columnObj.getInt(MetaData::ATTR_DATA_TYPE))<<endl;
   .
   .
   .
   /* and so on to obtain metadata on other column specific attributes */
}

The following code example demonstrates how to obtain metadata about a database table with a column containing a user-defined type:

/* Create an environment and a connection to the HR database */
.
.
.
/* Call the getMetaData method on the Connection object obtained */
MetaData custtab_metaData = connection->getMetaData("CUSTOMERS",
   MetaData::PTYPE_TABLE);

/* Now that you have the metadata information on the CUSTOMERS table,
   call the getxxx methods using the appropriate attributes
*/
/* Call getString */
cout<<"Schema:"<<(custtab_metaData.getString(MetaData::ATTR_OBJ_SCHEMA))<<endl;

if(custtab_metaData.getInt(custtab_metaData::ATTR_PTYPE)==MetaData::PTYPE_TABLE)
   cout<<"CUSTOMERS is a table"<<endl;
else
   cout<<"CUSTOMERS is not a table"<<endl;

/* Call getVector to obtain a list of columns in the CUSTOMERS table */
vector<MetaData>listOfColumns;
listOfColumns=custtab_metaData.getVector(MetaData::ATTR_LIST_COLUMNS);

/* Assuming that the metadata for the column cust_address_typ
   is the fourth element in the list...
*/
MetaData customer_address=listOfColumns[3];

/* Now you can obtain the metadata for the customer_address attribute */
int typcode = customer_address.getInt(MetaData::ATTR_TYPECODE);
if(typcode==OCCI_TYPECODE_OBJECT)
   cout<<"customer_address is an object type"<<endl;
else
   cout<<"customer_address is not an object type"<<endl;

string objectName=customer_address.getString(MetaData::ATTR_OBJ_NAME);

/* Now that you have the name of the address object,
   the metadata of the attributes of the type can be obtained by using
   getMetaData on the connection by passing the object name
*/
MetaData address = connection->getMetaData(objectName);

/* Call getVector to obtain the list of the address object attributes */
vector<MetaData> attributeList =
                 address.getVector(MetaData::ATT_LIST_TYPE_ATTRS);

/* and so on to obtain metadata on other address object specific attributes */

The following code example demonstrates how to obtain metadata about an object when using a reference to it:

Assuming the following schema structure:

Type ADDRESS(street VARCHAR2(50), city VARCHAR2(20));
Table Person(id NUMBER, addr REF ADDRESS);

/* Create an environment and a connection to the HR database */
.
.
.
/* Call the getMetaData method on the Connection object obtained */
MetaData perstab_metaData = connection->getMetaData("Person",
   MetaData::PTYPE_TABLE);

/* Now that you have the metadata information on the Person table,
   call the getxxx methods using the appropriate attributes
*/
/* Call getString */
cout<<"Schema:"<<(perstab_metaData.getString(MetaData::ATTR_OBJ_SCHEMA))<<endl;

if(perstab_metaData.getInt(perstab_metaData::ATTR_PTYPE)==MetaData::PTYPE_TABLE)
   cout<<"Person is a table"<<endl;
else
   cout<<"Person is not a table"<<endl;

/* Call getVector to obtain the list of columns in the Person table
*/
vector<MetaData>listOfColumns;
listOfColumns=perstab_metaData.getVector(MetaData::ATTR_LIST_COLUMNS);

/* Each of the list elements represents a column metadata,
   so now get the datatype of the column by passing ATTR_DATA_TYPE
   to getInt
*/
for(int i=0;i<numCols;i++)
{
int dataType=colList[i].getInt(MetaData::ATTR_DATA_TYPE);
/* If the datatype is a reference, get the Ref and obtain the metadata
   about the object by passing the Ref to getMetaData
*/
if(dataType==SQLT_REF)
   RefAny refTdo=colList[i].getRef(MetaData::ATTR_REF_TDO);

/* Now you can obtain the metadata about the object as shown
MetaData tdo_metaData=connection->getMetaData(refTdo);

/* Now that you have the metadata about the TDO, you can obtain the metadata
   about the object
*/

Resultset Metadata Code Example

The following code example demonstrates how to obtain metadata about a select list from a ResultSet object:

/* Create an environment and a connection to the database */
.
.
.
/* Create a statement and associate it with a select clause */
string sqlStmt="SELECT * FROM EMPLOYEES";
Statement *stmt=conn->createStatement(sqlStmt);

/* Execute the statement to obtain a ResultSet */
ResultSet *rset=stmt->executeQuery();

/* Obtain the metadata about the select list */
vector<MetaData>cmd=rset->getColumnListMetaData();

/* The metadata is a column list and each element is a column metaData */
int dataType=cmd[i].getInt(MetaData::ATTR_DATA_TYPE);
.
.
.

The getMetaData method is called for the ATTR_COLLECTION_ELEMENT attribute only.

Attribute Reference

This section describes the attributes belonging to schema and subschema objects. The following attribute groupings are presented:

Parameter Attributes

All elements have some attributes specific to that element and some generic attributes. Table 6-2 describes the attributes that belong to all elements:

Table 6-2 Attributes Belonging to All Elements

Attribute	Description	Attribute Datatype
`ATTR_OBJ_ID`	Object or schema ID	`unsigned int`
`ATTR_OBJ_NAME`	Object, schema, or database name	`string`
`ATTR_OBJ_SCHEMA`	Schema where object is located	`string`
`ATTR_OBJ_PTYPE`	Type of information described by the parameter The possible values are: `PTYPE_TABLE`, Table `PTYPE_VIEW`, View `PTYPE_PROC`, Procedure `PTYPE_FUNC`, Function `PTYPE_PKG`, Package `PTYPE_TYPE`, Type `PTYPE_TYPE_ATTR`, Attribute of a type `PTYPE_TYPE_COLL`, Collection type information `PTYPE_TYPE_METHOD`, A method of a type `PTYPE_SYN`, Synonym `PTYPE_SEQ`, equence `PTYPE_COL`, Column of a table or view `PTYPE_ARG`, Argument of a function or procedure `PTYPE_TYPE_ARG`, Argument of a type method `PTYPE_TYPE_RESULT`, Results of a method `PTYPE_SCHEMA`, Schema `PTYPE_DATABASE`, Database	`int`
`ATTR_TIMESTAMP`	The `TIMESTAMP` of the object this description is based on (Oracle DATE format)	`Timestamp`

The sections that follow list attributes specific to different types of elements.

Table and View Attributes

A parameter for a table or view (type PTYPE_TABLE or PTYPE_VIEW) has the following type-specific attributes described in Table 6-3:

Table 6-3 Attributes Belonging to Tables or Views

Attribute	Description	Attribute Datatype
`ATTR_OBJID`	Object ID	`unsigned int`
`ATTR_NUM_COLS`	Number of columns	`int`
`ATTR_LIST_COLUMNS`	Column list (type `PTYPE_LIST`)	`vector<MetaData>`
`ATTR_REF_TDO`	`REF` to the `TDO` of the base type in case of extent tables	`RefAny`
`ATTR_IS_TEMPORARY`	Identifies whether the table or view is temporary	`bool`
`ATTR_IS_TYPED`	Identifies whether the table or view is typed	`bool`
`ATTR_DURATION`	Duration of a temporary table. Values can be: `OCCI_DURATION_SESSION` (session) `OCCI_DURATION_TRANS` (transaction) `OCCI_DURATION_NULL` (table not temporary)	`int`

The additional attributes belonging to tables are described in Table 6-4.

Table 6-4 Attributes Specific to Tables

Attribute	Description	Attribute Datatype
`ATTR_DBA`	Data block address of the segment header	`unsigned int`
`ATTR_TABLESPACE`	Tablespace the table resides on	`int`
`ATTR_CLUSTERED`	Identifies whether the table is clustered	`bool`
`ATTR_PARTITIONED`	Identifies whether the table is partitioned	`bool`
`ATTR_INDEX_ONLY`	Identifies whether the table is index only	`bool`

Procedure, Function, and Subprogram Attributes

A parameter for a procedure or function (type PTYPE_PROC or PTYPE_FUNC) has the type-specific attributes described in Table 6-5.

Table 6-5 Attributes Belonging to Procedures or Functions

Attribute Description Attribute Datatype

Attribute	Description	Attribute Datatype
`ATTR_LIST_ARGUMENTS`	Argument list Refer to List Attributes .	`vector<MetaData>`
`ATTR_IS_INVOKER_RIGHTS`	Identifies whether the procedure or function has invoker-rights.	`int`

ATTR_LIST_ARGUMENTS

Argument list

Refer to List Attributes .

vector<MetaData>

ATTR_IS_INVOKER_RIGHTS

Identifies whether the procedure or function has invoker-rights.

int

The additional attributes belonging to package subprograms are described in Table 6-6.

Table 6-6 Attributes Belonging to Package Subprograms

Attribute	Description	Attribute Datatype
`ATTR_NAME`	Name of procedure or function	`string`
`ATTR_OVERLOAD_ID`	Overloading ID number (relevant in case the procedure or function is part of a package and is overloaded). Values returned may be different from direct query of a PL/SQL function or procedure.	`int`

Package Attributes

A parameter for a package (type PTYPE_PKG) has the type-specific attributes described in Table 6-7.

Table 6-7 Attributes Belonging to Packages

Attribute Description Attribute Datatype

Attribute	Description	Attribute Datatype
`ATTR_LIST_SUBPROGRAMS`	Subprogram list Refer to List Attributes .	`vector<MetaData>`
`ATTR_IS_INVOKER_RIGHTS`	Identifies whether the package has invoker-rights	`bool`

ATTR_LIST_SUBPROGRAMS

Subprogram list

Refer to List Attributes .

vector<MetaData>

ATTR_IS_INVOKER_RIGHTS

Identifies whether the package has invoker-rights

bool

Type Attributes

A parameter for a type (type PTYPE_TYPE) has attributes described in Table 6-8.

Table 6-8 Attributes Belonging to Types

Attribute	Description	Attribute Datatype
`ATTR_REF_TDO`	Returns the in-memory ref of the type descriptor object for the type, if the column type is an object type.	`RefAny`
`ATTR_TYPECODE`	Typecode. Can be `OCCI_TYPECODE_OBJECT` or `OCCI_TYPECODE_NAMEDCOLLECTION`. Refer to Notes on Types and Attributes .	`int`
`ATTR_COLLECTION_TYPECODE`	Typecode of collection if type is collection; invalid otherwise. Can be `OCCI_TYPECODE_VARRAY` or `OCCI_TYPECODE_TABLE`. Refer to Notes on Types and Attributes .	`int`
`ATTR_VERSION`	A null terminated string containing the user-assigned version	`string`
`ATTR_IS_FINAL_TYPE`	Identifies whether this is a final type	bool
`ATTR_IS_INSTANTIABLE_TYPE`	Identifies whether this is an instantiable type	bool
`ATTR_IS_SUBTYPE`	Identifies whether this is a subtype	bool
`ATTR_SUPERTYPE_SCHEMA_NAME`	Name of the schema containing the supertype	string
`ATTR_SUPERTYPE_NAME`	Name of the supertype	string
`ATTR_IS_INVOKER_RIGHTS`	Identifies whether this type is invoker-rights	`bool`
`ATTR_IS_INCOMPLETE_TYPE`	Identifies whether this type is incomplete	`bool`
`ATTR_IS_SYSTEM_TYPE`	Identifies whether this is a system type	`bool`
`ATTR_IS_PREDEFINED_TYPE`	Identifies whether this is a predefined type	`bool`
`ATTR_IS_TRANSIENT_TYPE`	Identifies whether this is a transient type	`bool`
`ATTR_IS_SYSTEM_GENERATED_TYPE`	Identifies whether this is a system-generated type	`bool`
`ATTR_HAS_NESTED_TABLE`	Identifies whether this type contains a nested table attribute	`bool`
`ATTR_HAS_LOB`	Identifies whether this type contains a LOB attribute	`bool`
`ATTR_HAS_FILE`	Identifies whether this type contains a FILE attribute	`bool`
`ATTR_COLLECTION_ELEMENT`	Handle to collection element Refer to Collection Attributes	`MetaData`
`ATTR_NUM_TYPE_ATTRS`	Number of type attributes	`unsigned int`
`ATTR_LIST_TYPE_ATTRS`	List of type attributes Refer to List Attributes	`vector<MetaData>`
`ATTR_NUM_TYPE_METHODS`	Number of type methods	`unsigned int`
`ATTR_LIST_TYPE_METHODS`	List of type methods Refer to List Attributes	`vector<MetaData>`
`ATTR_MAP_METHOD`	Map method of type Refer to Type Method Attributes	`MetaData`
`ATTR_ORDER_METHOD`	Order method of type Refer to Type Method Attributes	`MetaData`

Type Attribute Attributes

A parameter for an attribute of a type (type PTYPE_TYPE_ATTR) has the attributes described in Table 6-9.

Table 6-9 Attributes Belonging to Type Attributes

Attribute	Description	Attribute Datatype
`ATTR_DATA_SIZE`	Maximum size of the type attribute. This length is returned in bytes and not characters for strings and raws. Returns 22 for `NUMBER`.	`int`
`ATTR_TYPECODE`	Typecode Refer to Notes on Types and Attributes .	`int`
`ATTR_DATA_TYPE`	Datatype of the type attribute Refer to Notes on Types and Attributes .	`int`
`ATTR_NAME`	A pointer to a string that is the type attribute name	`string`
`ATTR_PRECISION`	Precision of numeric type attributes. If the precision is nonzero and scale is -127, then it is a FLOAT; otherwise a `NUMBER`(p, s). If precision is 0, then `NUMBER`(p, s) can be represented simply by `NUMBER`.	`int`
`ATTR_SCALE`	Scale of numeric type attributes. If the precision is nonzero and scale is -127, then it is a `FLOAT`; otherwise a `NUMBER`(p, s). If precision is 0, then `NUMBER`(p, s) can be represented simply as `NUMBER`.	`int`
`ATTR_TYPE_NAME`	A string that is the type name. The returned value will contain the type name if the datatype is `SQLT_NTY` or `SQLT_REF`. If the datatype is `SQLT_NTY`, then the name of the named datatype's type is returned. If the datatype is `SQLT_REF`, then the type name of the named datatype pointed to by the `REF` is returned.	`string`
`ATTR_SCHEMA_NAME`	String with the schema name under which the type has been created	`string`
`ATTR_REF_TDO`	Returns the in-memory `REF` of the TDO for the type, if the column type is an object type.	`RefAny`
`ATTR_CHARSET_ID`	Character set ID, if the type attribute is of a string or character type	`int`
`ATTR_CHARSET_FORM`	Character set form, if the type attribute is of a string or character type	`int`
`ATTR_FSPRECISION`	The fractional seconds precision of a datetime or interval	`int`
`ATTR_LFPRECISION`	The leading field precision of an interval	`int`

Type Method Attributes

A parameter for a method of a type (type PTYPE_TYPE_METHOD) has the attributes described in Table 6-10.

Table 6-10 Attributes Belonging to Type Methods

Attribute	Description	Attribute Datatype
`ATTR_NAME`	Name of method (procedure or function)	`string`
`ATTR_ENCAPSULATION`	Encapsulation level of the method (either `OCCI_TYPEENCAP_PRIVATE` or `OCCI_TYPEENCAP_PUBLIC`)	`int`
`ATTR_LIST_ARGUMENTS`	Argument list	`vector<MetaData>`
`ATTR_IS_CONSTRUCTOR`	Identifies whether the method is a constructor	`bool`
`ATTR_IS_DESTRUCTOR`	Identifies whether the method is a destructor	`bool`
`ATTR_IS_OPERATOR`	Identifies whether the method is an operator	`bool`
`ATTR_IS_SELFISH`	Identifies whether the method is selfish	`bool`
`ATTR_IS_MAP`	Identifies whether the method is a map method	`bool`
`ATTR_IS_ORDER`	Identifies whether the method is an order method	`bool`
`ATTR_IS_RNDS`	Identifies whether "Read No Data State" is set for the method	`bool`
`ATTR_IS_RNPS`	Identifies whether "Read No Process State" is set for the method	`bool`
`ATTR_IS_WNDS`	Identifies whether "Write No Data State" is set for the method	`bool`
`ATTR_IS_WNPS`	Identifies whether "Write No Process State" is set for the method	`bool`
`ATTR_IS_FINAL_METHOD`	Identifies whether this is a final method	`bool`
`ATTR_IS_INSTANTIABLE_METHOD`	Identifies whether this is an instantiable method	`bool`
`ATTR_IS_OVERRIDING_METHOD`	Identifies whether this is an overriding method	`bool`

Collection Attributes

A parameter for a collection type (type PTYPE_COLL) has the attributes described in Table 6-11.

Table 6-11 Attributes Belonging to Collection Types

Attribute	Description	Attribute Datatype
`ATTR_DATA_SIZE`	Maximum size of the type attribute. This length is returned in bytes and not characters for strings and raws. Returns `22` for `NUMBER`.	`int`
`ATTR_TYPECODE`	Typecode Refer to Notes on Types and Attributes .	`int`
`ATTR_DATA_TYPE`	The datatype of the type attribute Refer to Notes on Types and Attributes .	`int`
`ATTR_NUM_ELEMENTS`	Number of elements in an array. Only valid for collections that are arrays.	`unsigned int`
`ATTR_NAME`	A pointer to a string that is the type attribute name	`string`
`ATTR_PRECISION`	Precision of numeric type attributes. If the precision is nonzero and scale is `-127`, then it is a `FLOAT`; otherwise a `NUMBER(p, s)`. If precision is `0`, then `NUMBER(p, s)` can be represented simply as `NUMBER`.	`int`
`ATTR_SCALE`	Scale of numeric type attributes. If the precision is nonzero and scale is `-127`, then it is a `FLOAT`; otherwise a `NUMBER(p, s)`. If precision is `0`, then `NUMBER(p, s)` can be represented simply as `NUMBER`.	`int`
`ATTR_TYPE_NAME`	String that is the type name. The returned value will contain the type name if the datatype is `SQLT_NTY` or `SQLT_REF`. If the datatype is `SQLT_NTY`, then the name of the named datatype's type is returned. If the datatype is `SQLT_REF`, then the type name of the named datatype pointed to by the `REF` is returned	`string`
`ATTR_SCHEMA_NAME`	String with the schema name under which the type has been created	`string`
`ATTR_REF_TDO`	Maximum size of the type attribute. This length is returned in bytes and not characters for strings and raws. Returns `22` for `NUMBER`.	`RefAny`
`ATTR_CHARSET_ID`	Typecode Refer to Notes on Types and Attributes .	`int`
`ATTR_CHARSET_FORM`	The datatype of the type attribute Refer to Notes on Types and Attributes .	`int`

Synonym Attributes

A parameter for a synonym (type PTYPE_SYN) has the attributes described in Table 6-12.

Table 6-12 Attributes Belonging to Synonyms

Attribute	Description	Attribute Datatype
`ATTR_OBJID`	Object ID	`unsigned int`
`ATTR_SCHEMA_NAME`	Null-terminated string containing the schema name of the synonym translation	`string`
`ATTR_NAME`	Null-terminated string containing the object name of the synonym translation	`string`
`ATTR_LINK`	Null-terminated string containing the database link name of the synonym translation	`string`

Sequence Attributes

A parameter for a sequence (type PTYPE_SEQ) has the attributes described in Table 6-13.

Table 6-13 Attributes Belonging to Sequences

Attribute	Description	Attribute Datatype
`ATTR_OBJID`	Object ID	`unsigned int`
`ATTR_MIN`	Minimum value (in Oracle number format)	`Number`
`ATTR_MAX`	Maximum value (in Oracle number format)	`Number`
`ATTR_INCR`	Increment (in Oracle number format)	`Number`
`ATTR_CACHE`	Number of sequence numbers cached; zero if the sequence is not a cached sequence (in Oracle number format)	`Number`
`ATTR_ORDER`	Identifies whether the sequence is ordered?	`bool`
`ATTR_HW_MARK`	High-water mark (in Oracle number format)	`Number`

Column Attributes

A parameter for a column of a table or view (type PTYPE_COL) has the attributes described in Table 6-14.

Table 6-14 Attributes Belonging to Columns of Tables or Views

Attribute	Description	Attribute Datatype
`ATTR_DATA_SIZE`	Column length in codepoints. The number of codepoints allowed in the column.	`int`
`ATTR_DATA_TYPE`	Type of length semantics of the column. Valid values are 0 for byte-length semantics and 1 for codepoint-length semantics.	`int`
`ATTR_NAME`	Maximum size of the column. This length is returned in bytes and not characters for strings and raws. Returns `22` for `NUMBER`.	`string`
`ATTR_PRECISION`	The datatype of the column Refer to Notes on Types and Attributes .	`int`
`ATTR_SCALE`	Pointer to a string that is the column name	`int`
`ATTR_IS_NULL`	The precision of numeric columns. If the precision is nonzero and scale is `-127`, then it is a `FLOAT`; otherwise a `NUMBER(p, s)`. If precision is `0`, `NUMBER(p, s)` can be represented simply as `NUMBER`.	`bool`
`ATTR_TYPE_NAME`	Scale of numeric columns. If the precision is nonzero and scale is `-127`, then it is a `FLOAT`; otherwise a `NUMBER(p, s)`. If precision is `0`, then `NUMBER(p, s)` can be represented simply as `NUMBER`.	`string`
`ATTR_SCHEMA_NAME`	Returns `0` if null values are not permitted for the column	`string`
`ATTR_REF_TDO`	Returns a string that is the type name. The returned value will contain the type name if the datatype is `SQLT_NTY` or `SQLT_REF`. If the datatype is `SQLT_NTY`, then the name of the named datatype's type is returned. If the datatype is `SQLT_REF`, then the type name of the named datatype pointed to by the `REF` is returned	`RefAny`
`ATTR_CHARSET_ID`	Returns a string with the schema name under which the type has been created	`int`
`ATTR_CHARSET_FORM`	`REF` of the `TDO` for the type, if the column type is an object type	`int`

Argument and Result Attributes

A parameter for an argument or a procedure or function type (type PTYPE_ARG), for a type method argument (type PTYPE_TYPE_ARG), or for method results (type PTYPE_TYPE_RESULT) has the attributes described in Table 6-15.

Table 6-15 Attributes Belonging to Arguments / Results

Attribute	Description	Attribute Datatype
`ATTR_NAME`	Returns a pointer to a string which is the argument name	`string`
`ATTR_POSITION`	Position of the argument in the argument list. Always returns `0`.	`int`
`ATTR_TYPECODE`	Typecode Refer to Notes on Types and Attributes .	`int`
`ATTR_DATA_TYPE`	Datatype of the argument Refer to Notes on Types and Attributes .	`int`
`ATTR_DATA_SIZE`	Size of the datatype of the argument. This length is returned in bytes and not characters for strings and raws. Returns `22` for `NUMBER`.	`int`
`ATTR_PRECISION`	Precision of numeric arguments. If the precision is nonzero and scale`-127`, then it is a `FLOAT`; otherwise a `NUMBER(p, s)`. If precision is `0`, then `NUMBER(p, s)` can be represented simply as `NUMBER`.	`int`
`ATTR_SCALE`	Scale of numeric arguments. If the precision is nonzero and scale`-127`, then it is a `FLOAT`; otherwise a `NUMBER(p, s)`. If precision is `0`, then `NUMBER(p, s)` can be represented simply as `NUMBER`.	`int`
`ATTR_LEVEL`	Datatype levels. This attribute always returns `0`.	`int`
`ATTR_HAS_DEFAULT`	Indicates whether an argument has a default	`int`
`ATTR_LIST_ARGUMENTS`	The list of arguments at the next level (when the argument is of a record or table type)	`vector<MetaData>`
`ATTR_IOMODE`	Indicates the argument mode. Valid values are `0` for `IN (OCCI_TYPEPARAM_IN)`, `1` for `OUT (OCCI_TYPEPARAM_OUT)`, and `2` for `IN/OUT (OCCI_TYPEPARAM_INOUT)`	`int`
`ATTR_RADIX`	Returns a radix (if number type)	`int`
`ATTR_IS_NULL`	Returns `0` if null values are not permitted for the column	`int`
`ATTR_TYPE_NAME`	Returns a string that is the type name, or the package name in the case of package local types. The returned value contains the type name if the datatype is `SQLT_NTY` or `SQLT_REF`. If the datatype is `SQLT_NTY`, then the name of the named datatype's type is returned. If the datatype is `SQLT_REF`, then the type name of the named datatype pointed to by the `REF` is returned.	`string`
`ATTR_SCHEMA_NAME`	For `SQLT_NTY` or `SQLT_REF`, returns a string with the schema name under which the type was created, or under which the package was created in the case of package local types	`string`
`ATTR_SUB_NAME`	For `SQLT_NTY` or `SQLT_REF`, returns a string with the type name, in the case of package local types	`string`
`ATTR_LINK`	For `SQLT_NTY` or `SQLT_REF`, returns a string with the database link name of the database on which the type exists. This can happen only in the case of package local types, when the package is remote.	`string`
`ATTR_REF_TDO`	Returns the `REF` of the `TDO` for the type, if the argument type is an object	`RefAny`
`ATTR_CHARSET_ID`	Returns the character set `ID` if the argument is of a string or character type	`int`
`ATTR_CHARSET_FORM`	Returns the character set form if the argument is of a string or character type	`int`

List Attributes

A list type of attribute can be described for all the elements in the list. In case of a function argument list, position 0 has a parameter for return values (PTYPE_ARG).

The list is described iteratively for all the elements. The results are stored in a C++ vector<MetaData>. Call the getVector method to describe list type of attributes. Table 6-16 displays the list attributes.

Table 6-16 Values for ATTR_LIST_TYPE

Possible Values	Description
`ATTR_LIST_COLUMNS`	Column list
`ATTR_LIST_ARGUMENTS`	Procedure or function arguments list
`ATTR_LIST_SUBPROGRAMS`	Subprogram list
`ATTR_LIST_TYPE_ATTRIBUTES`	Type attribute list
`ATTR_LIST_TYPE_METHODS`	Type method list
`ATTR_LIST_OBJECTS`	Object list within a schema
`ATTR_LIST_SCHEMAS`	Schema list within a database

Schema Attributes

A parameter for a schema type (type PTYPE_SCHEMA) has the attributes described in Table 6-17.

Table 6-17 Attributes Specific to Schemas

Attribute	Description	Attribute Datatype
`ATTR_LIST_OBJECTS`	List of objects in the schema	`string`

Database Attributes

A parameter for a database (type PTYPE_DATABASE) has the attributes described in Table 6-18.

Table 6-18 Attributes Specific to Databases

Attribute	Description	Attribute Datatype
`ATTR_VERSION`	Database version	`string`
`ATTR_CHARSET_ID`	Database character set ID from the server handle	`int`
`ATTR_NCHARSET_ID`	Database native character set ID from the server handle	`int`
`ATTR_LIST_SCHEMAS`	List of schemas (type PTYPE_SCHEMA) in the database	`vector<MetaData>`
`ATTR_MAX_PROC_LEN`	Maximum length of a procedure name	`unsigned int`
`ATTR_MAX_COLUMN_LEN`	Maximum length of a column name	`unsigned int`
`ATTR_CURSOR_COMMIT_BEHAVIOR`	How a `COMMIT` operation affects cursors and prepared statements in the database. Values are: `OCCI_CURSOR_OPEN` for preserving cursor state as before the commit operation and `OCCI_CURSOR_CLOSED` for cursors that are closed on `COMMIT`, although the application can still reexecute the statement without preparing it again.	`int`
`ATTR_MAX_CATALOG_NAMELEN`	Maximum length of a catalog (database) name	`int`
`ATTR_CATALOG_LOCATION`	Position of the catalog in a qualified table. Valid values are `OCCI_CL_START` and `OCCI_CL_END`.	`int`
`ATTR_SAVEPOINT_SUPPORT`	Identifies whether the database supports savepoints. Valid values are `OCCI_SP_SUPPORTED` and `OCCI_SP_UNSUPPORTED`.	`int`
`ATTR_NOWAIT_SUPPORT`	Identifies whether the database supports the nowait clause. Valid values are `OCCI_NW_SUPPORTED` and `OCCI_NW_UNSUPPORTED`.	`int`
`ATTR_AUTOCOMMIT_DDL`	Identifies whether the autocommit mode is required for DDL statements. Valid values are `OCCI_AC_DDL` and `OCCI_NO_AC_DDL`.	`int`
`ATTR_LOCKING_MODE`	Locking mode for the database. Valid values are `OCCI_LOCK_IMMEDIATE` and `OCCI_LOCK_DELAYED`.	`int`

See Also:

Appendix A, "OCCI Demonstration Programs" and the code example occidesc.cpp for an illustration of the concepts covered in this chapter

6 Metadata