# 7. API: Cursor Objects

A cursor object can be created with `Connection.cursor()`.

## 7.1. Cursor Methods

Cursor.__enter__()

  The entry point for the cursor as a context manager. It returns itself.

  Note

  This method is an extension to the DB API definition.

Cursor.__exit__()

  The exit point for the cursor as a context manager. It closes the cursor.

  Note

  This method is an extension to the DB API definition.

Cursor.arrayvar(typ, value[, size])

  Creates an array variable associated with the cursor of the given type and size and return a variable object. The value is either an integer specifying the number of elements to allocate or it is a list and the number of elements allocated is drawn from the size of the list. If the value is a list, the variable is also set with the contents of the list. If the size is not specified and the type is a string or binary, 4000 bytes is allocated. This is needed for passing arrays to PL/SQL (in cases where the list might be empty and the type cannot be determined automatically) or returning arrays from PL/SQL.

  Array variables can only be used for PL/SQL associative arrays with contiguous keys. For PL/SQL associative arrays with sparsely populated keys or for varrays and nested tables, the approach shown in this example needs to be used.

  Note

  The DB API definition does not define this method.

Cursor.bindnames()

  Returns the list of bind variable names bound to the statement. Note that a statement must have been prepared first.

  Note

  The DB API definition does not define this method.

Cursor.callfunc(name, returnType, parameters=[], keyword_parameters={})

  Calls a function with the given name. The return type is specified in the same notation as is required by `setinputsizes()`. The sequence of parameters must contain one entry for each parameter that the function expects. Any keyword parameters will be included after the positional parameters. The result of the call is the return value of the function.

  See PL/SQL Stored Functions for an example.

  For consistency and compliance with the PEP 8 naming style, the parameter keywordParameters was renamed to keyword_parameters. The old name will continue to work as a keyword parameter for a period of time.

  Note

  The DB API definition does not define this method.

  Note

  If you intend to call `Cursor.setinputsizes()` on the cursor prior to making this call, then note that the first item in the parameter list refers to the return value of the function.

Cursor.callproc(name, parameters=[], keyword_parameters={})

  Calls a procedure with the given name. The sequence of parameters must contain one entry for each parameter that the procedure expects. The result of the call is a modified copy of the input sequence. Input parameters are left untouched; output and input/output parameters are replaced with possibly new values. Keyword parameters will be included after the positional parameters and are not returned as part of the output sequence.

  See PL/SQL Stored Procedures for an example.

  For consistency and compliance with the PEP 8 naming style, the parameter keywordParameters was renamed to keyword_parameters. The old name will continue to work as a keyword parameter for a period of time.

  Note

  The DB API definition does not allow for keyword parameters.

Cursor.close()

  Closes the cursor now, rather than whenever __del__ is called. The cursor will be unusable from this point forward; an Error exception will be raised if any operation is attempted with the cursor.

Cursor.execute(statement, parameters=[], **keyword_parameters)

  Executes a statement against the database. See Executing SQL.

  Parameters may be passed as a dictionary or sequence or as keyword parameters. If the parameters are a dictionary, the values will be bound by name and if the parameters are a sequence the values will be bound by position. Note that if the values are bound by position, the order of the variables is from left to right as they are encountered in the statement and SQL statements are processed differently than PL/SQL statements. For this reason, it is generally recommended to bind parameters by name instead of by position.

  Parameters passed as a dictionary are name and value pairs. The name maps to the bind variable name used by the statement and the value maps to the Python value you wish bound to that bind variable.

  A reference to the statement will be retained by the cursor. If None or the same string object is passed in again, the cursor will execute that statement again without performing a prepare or rebinding and redefining. This is most effective for algorithms where the same statement is used, but different parameters are bound to it (many times). Note that parameters that are not passed in during subsequent executions will retain the value passed in during the last execution that contained them.

  For maximum efficiency when reusing an statement, it is best to use the `setinputsizes()` method to specify the parameter types and sizes ahead of time; in particular, None is assumed to be a string of length 1 so any values that are later bound as numbers or dates will raise a TypeError exception.

  If the statement is a query, the cursor is returned as a convenience to the caller (so it can be used directly as an iterator over the rows in the cursor); otherwise, `None` is returned.

  Note

  The DB API definition does not define the return value of this method.

Cursor.executemany(statement, parameters, batcherrors=False, arraydmlrowcounts=False)

  Prepares a statement for execution against a database and then execute it against all parameter mappings or sequences found in the sequence parameters. See Executing Batch Statements and Bulk Loading.

  The `statement` parameter is managed in the same way as the `execute()` method manages it. If the size of the buffers allocated for any of the parameters exceeds 2 GB, you will receive the error “DPI-1015: array size of <n> is too large”, where <n> varies with the size of each element being allocated in the buffer. If you receive this error, decrease the number of elements in the sequence parameters.

  If there are no parameters, or parameters have previously been bound, the number of iterations can be specified as an integer instead of needing to provide a list of empty mappings or sequences.

  When True, the `batcherrors` parameter enables batch error support within Oracle and ensures that the call succeeds even if an exception takes place in one or more of the sequence of parameters. The errors can then be retrieved using `getbatcherrors()`.

  When True, the `arraydmlrowcounts` parameter enables DML row counts to be retrieved from Oracle after the method has completed. The row counts can then be retrieved using `getarraydmlrowcounts()`.

  Both the `batcherrors` parameter and the `arraydmlrowcounts` parameter can only be true when executing an insert, update, delete or merge statement; in all other cases an error will be raised.

  For maximum efficiency, it is best to use the `setinputsizes()` method to specify the parameter types and sizes ahead of time; in particular, None is assumed to be a string of length 1 so any values that are later bound as numbers or dates will raise a TypeError exception.

Cursor.fetchall()

  Fetches all (remaining) rows of a query result, returning them as a list of tuples. An empty list is returned if no more rows are available. Note that the cursor’s arraysize attribute can affect the performance of this operation, as internally reads from the database are done in batches corresponding to the arraysize.

  An exception is raised if the previous call to `execute()` did not produce any result set or no call was issued yet.

  See Fetch Methods for an example.

Cursor.fetchmany(size=cursor.arraysize)

  Fetches the next set of rows of a query result, returning a list of tuples. An empty list is returned if no more rows are available. Note that the cursor’s arraysize attribute can affect the performance of this operation.

  The number of rows to fetch is specified by the parameter. If it is not given, the cursor’s arraysize attribute determines the number of rows to be fetched. If the number of rows available to be fetched is fewer than the amount requested, fewer rows will be returned.

  An exception is raised if the previous call to `execute()` did not produce any result set or no call was issued yet.

  See Fetch Methods for an example.

Cursor.fetchone()

  Fetches the next row of a query result set, returning a single tuple or None when no more data is available.

  An exception is raised if the previous call to `execute()` did not produce any result set or no call was issued yet.

  See Fetch Methods for an example.

Cursor.getarraydmlrowcounts()

  Retrieves the DML row counts after a call to `executemany()` with arraydmlrowcounts enabled. This will return a list of integers corresponding to the number of rows affected by the DML statement for each element of the array passed to `executemany()`.

  Note

  The DB API definition does not define this method and it is only available for Oracle 12.1 and higher.

Cursor.getbatcherrors()

  Retrieves the exceptions that took place after a call to `executemany()` with batcherrors enabled. This will return a list of Error objects, one error for each iteration that failed. The offset can be determined by looking at the offset attribute of the error object.

  Note

  The DB API definition does not define this method.

Cursor.getimplicitresults()

  Returns a list of cursors which correspond to implicit results made available from a PL/SQL block or procedure without the use of OUT ref cursor parameters. The PL/SQL block or procedure opens the cursors and marks them for return to the client using the procedure dbms_sql.return_result. Cursors returned in this fashion should not be closed. They will be closed automatically by the parent cursor when it is closed. Closing the parent cursor will invalidate the cursors returned by this method.

  Note

  The DB API definition does not define this method and it is only available for Oracle Database 12.1 (both client and server must be at this level or higher). It is most like the DB API method nextset(), but unlike that method (which requires that the next result set overwrite the current result set), this method returns cursors which can be fetched independently of each other.

Cursor.__iter__()

  Returns the cursor itself to be used as an iterator.

  Note

  This method is an extension to the DB API definition but it is mentioned in PEP 249 as an optional extension.

Cursor.parse(statement)

  This can be used to parse a statement without actually executing it (this step is done automatically by Oracle when a statement is executed).

  Note

  The DB API definition does not define this method.

  Note

  You can parse any DML or DDL statement. DDL statements are executed immediately and an implied commit takes place.

Cursor.prepare(statement, tag, cache_statement=True)

  This can be used before a call to `execute()` to define the statement that will be executed. When this is done, the prepare phase will not be performed when the call to `execute()` is made with None or the same string object as the statement.

  If the `tag` parameter is specified and the `cache_statement` parameter is True, the statement will be returned to the statement cache with the given tag.

  If the `cache_statement` parameter is False, the statement will be removed from the statement cache (if it was found there) or will simply not be cached.

  See Statement Caching for more information.

  Note

  The DB API definition does not define this method.

Cursor.scroll(value=0, mode='relative')

  Scrolls the cursor in the result set to a new position according to the mode.

  If mode is “relative” (the default value), the value is taken as an offset to the current position in the result set. If set to “absolute”, value states an absolute target position. If set to “first”, the cursor is positioned at the first row and if set to “last”, the cursor is set to the last row in the result set.

  An error is raised if the mode is “relative” or “absolute” and the scroll operation would position the cursor outside of the result set.

  Note

  This method is an extension to the DB API definition but it is mentioned in PEP 249 as an optional extension.

Cursor.setinputsizes(\*args, \*\*keywordArgs)

  This can be used before a call to `execute()`, `callfunc()` or `callproc()` to predefine memory areas for the operation’s parameters. Each parameter should be a type object corresponding to the input that will be used or it should be an integer specifying the maximum length of a string parameter. Use keyword parameters when binding by name and positional parameters when binding by position. The singleton None can be used as a parameter when using positional parameters to indicate that no space should be reserved for that position.

  Note

  If you plan to use `callfunc()` then be aware that the first parameter in the list refers to the return value of the function.

Cursor.setoutputsize(size[, column])

  This method does nothing and is retained solely for compatibility with the DB API. The module automatically allocates as much space as needed to fetch LONG and LONG RAW columns (or CLOB as string and BLOB as bytes).

Cursor.var(typ[, size, arraysize, inconverter, outconverter, typename, encoding_errors, bypass_decode])

  Creates a variable with the specified characteristics. This method was designed for use with PL/SQL in/out variables where the length or type cannot be determined automatically from the Python object passed in or for use in input and output type handlers defined on cursors or connections.

  The `typ` parameter specifies the type of data that should be stored in the variable. This should be one of the database type constants, DB API constants, an object type returned from the method `Connection.gettype()` or one of the following Python types:

  Python Type | Database Type
  --- | ---
  bool | `oracledb.DB_TYPE_BOOLEAN`
  bytes | `oracledb.DB_TYPE_RAW`
  datetime.date | `oracledb.DB_TYPE_DATE`
  datetime.datetime | `oracledb.DB_TYPE_DATE`
  datetime.timedelta | `oracledb.DB_TYPE_INTERVAL_DS`
  decimal.Decimal | `oracledb.DB_TYPE_NUMBER`
  float | `oracledb.DB_TYPE_NUMBER`
  int | `oracledb.DB_TYPE_NUMBER`
  str | `oracledb.DB_TYPE_VARCHAR`

  The `size` parameter specifies the length of string and raw variables and is ignored in all other cases. If not specified for string and raw variables, the value 4000 is used.

  The `arraysize` parameter specifies the number of elements the variable will have. If not specified the bind array size (usually 1) is used. When a variable is created in an output type handler this parameter should be set to the cursor’s array size.

  The `inconverter` and `outconverter` parameters specify methods used for converting values to/from the database. More information can be found in the section on variable objects.

  The `typename` parameter specifies the name of a SQL object type and must be specified when using type `oracledb.OBJECT` unless the type object was passed directly as the first parameter.

  The `encoding_errors` parameter specifies what should happen when decoding byte strings fetched from the database into strings. It should be one of the values noted in the builtin decode function.

  The `bypass_decode` parameter, if specified, should be passed as a boolean value. Passing a True value causes values of database types `DB_TYPE_VARCHAR`, `DB_TYPE_CHAR`, `DB_TYPE_NVARCHAR`, `DB_TYPE_NCHAR` and `DB_TYPE_LONG` to be returned as bytes instead of str, meaning that python-oracledb does not do any decoding. See Fetching raw data for more information.

  For consistency and compliance with the PEP 8 naming style, the parameter encodingErrors was renamed to encoding_errors. The old name will continue to work as a keyword parameter for a period of time.

  Note

  The DB API definition does not define this method.

## 7.2. Cursor Attributes

Cursor.arraysize

  This read-write attribute can be used to tune the number of rows internally fetched and buffered by internal calls to the database when fetching rows from SELECT statements and REF CURSORS. The value can drastically affect the performance of a query since it directly affects the number of network round trips between Python and the database. For methods like `fetchone()` and `fetchall()` it does not change how many rows are returned to the application. For `fetchmany()` it is the default number of rows to fetch.

  The attribute is only used for tuning row and SODA document fetches from the database. It does not affect data inserts.

  Due to the performance benefits, the default `Cursor.arraysize` is 100 instead of the 1 that the Python DB API recommends.

  See Tuning Fetch Performance for more information.

Cursor.bindvars

  This read-only attribute provides the bind variables used for the last execute. The value will be either a list or a dictionary depending on whether binding was done by position or name. Care should be taken when referencing this attribute. In particular, elements should not be removed or replaced.

  Note

  The DB API definition does not define this attribute.

Cursor.connection

  This read-only attribute returns a reference to the connection object on which the cursor was created.

  Note

  This attribute is an extension to the DB API definition but it is mentioned in PEP 249 as an optional extension.

Cursor.description

  This read-only attribute is a sequence of 7-item sequences. Each of these sequences contains information describing one result column: (name, type, display_size, internal_size, precision, scale, null_ok). This attribute will be None for operations that do not return rows or if the cursor has not had an operation invoked via the `execute()` method yet.

  The type will be one of the database type constants defined at the module level.

Cursor.fetchvars

  This read-only attribute specifies the list of variables created for the last query that was executed on the cursor. Care should be taken when referencing this attribute. In particular, elements should not be removed or replaced.

  Note

  The DB API definition does not define this attribute.

Cursor.inputtypehandler

  This read-write attribute specifies a method called for each value that is bound to a statement executed on the cursor and overrides the attribute with the same name on the connection if specified. The method signature is handler(cursor, value, arraysize) and the return value is expected to be a variable object or None in which case a default variable object will be created. If this attribute is None, the default behavior will take place for all values bound to the statements.

  Note

  This attribute is an extension to the DB API definition.

Cursor.lastrowid

  This read-only attribute returns the rowid of the last row modified by the cursor. If no row was modified by the last operation performed on the cursor, the value None is returned.

Cursor.outputtypehandler

  This read-write attribute specifies a method called for each column that is to be fetched from this cursor. The method signature is handler(cursor, name, defaultType, length, precision, scale) and the return value is expected to be a variable object or None in which case a default variable object will be created. If this attribute is None, then the default behavior will take place for all columns fetched from this cursor.

  See Changing Fetched Data Types with Output Type Handlers.

  Note

  This attribute is an extension to the DB API definition.

Cursor.prefetchrows

  This read-write attribute can be used to tune the number of rows that the Oracle Client library fetches when a SELECT statement is executed. This value can reduce the number of round-trips to the database that are required to fetch rows but at the cost of additional memory. Setting this value to 0 can be useful when the timing of fetches must be explicitly controlled.

  The attribute is only used for tuning row fetches from the database. It does not affect data inserts.

  See Tuning Fetch Performance for more information.

  Note

  The DB API definition does not define this method.

Cursor.rowcount

  This read-only attribute specifies the number of rows that have currently been fetched from the cursor (for select statements), that have been affected by the operation (for insert, update, delete and merge statements), or the number of successful executions of the statement (for PL/SQL statements).

Cursor.rowfactory

  This read-write attribute specifies a method to call for each row that is retrieved from the database. Ordinarily, a tuple is returned for each row but if this attribute is set, the method is called with the tuple that would normally be returned, and the result of the method is returned instead.

  See Changing Query Results with Rowfactories.

  Note

  The DB API definition does not define this attribute.

Cursor.scrollable

  This read-write boolean attribute specifies whether the cursor can be scrolled or not. By default, cursors are not scrollable, as the server resources and response times are greater than nonscrollable cursors. This attribute is checked and the corresponding mode set in Oracle when calling the method `execute()`.

  Note

  The DB API definition does not define this attribute.

Cursor.statement

  This read-only attribute provides the string object that was previously prepared with `prepare()` or executed with `execute()`.

  Note

  The DB API definition does not define this attribute.