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

• Describing Database Metadata

• Attribute Reference

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 getxxx 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 obtained above */
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 above */
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 above */
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 below
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

• Table and View Attributes

• Procedure, Function, and Subprogram Attributes

• Package Attributes

• Type Attributes

• Type Attribute Attributes

• Type Method Attributes

• Collection Attributes

• Synonym Attributes

• Sequence Attributes

• Column Attributes

• Argument and Result Attributes

• List Attributes

• Schema Attributes

• Database Attributes

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. Possible Values	Description	int
	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	Sequence
	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
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
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
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. ADD MORE	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	The 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 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 arguments. 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_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