Inherits From:
EOAdaptorChannel : NSObject
Declared in:
InformixEOAdaptor/InformixChannel.h
InformixEOAdaptor/InformixDescription.h
The features InformixChannel adds to EOAdaptorChannel are as follows:
Generating Primary Keys
Each adaptor provides a database-specific implementation of the method primaryKeyForNewRowWithEntity: for generating primary keys. The InformixChannel's implementation uses a table named eo_sequence_table to keep track of the next available primary key value for a given table. The table contains a row for each table for which the adaptor provides primary key values. The statement used to create the eo_sequence_table is:
create table eo_sequence_table (
table_name varchar(32,0),
counter integer
)
InformixChannel uses a stored procedure named eo_pk_for_table to access and maintain the primary key counter in eo_sequence_table. The stored procedure is defined as follows:
create procedure
eo_pk_for_table (tname varchar(32))
returning int;
define cntr int;
update EO_SEQUENCE_TABLE
set COUNTER = COUNTER + 1
where TABLE_NAME = tname;
select COUNTER into cntr
from EO_SEQUENCE_TABLE
where TABLE_NAME = tname;
return cntr;
end procedure;
The stored procedure increments the counter in the eo_sequence_table row for the specified table, selects th counter value, and returns it. InformixChannel executes this eo_pk_for_table stored procedure from primaryKeyForNewRowWithEntity: and returns the stored procedure's return value.
To use InformixChannel's database-specific primary key generation mechanism, be sure that your database accommodates the adaptor's scheme. To modify your database so that it supports the adaptor's mechanism for generating primary keys, use EOModeler. For more information on this topic, see Enterprise Objects Framework Developer's Guide.
cursorDataArea
If the channel is connected, returns an Informix-specific data structure describing characteristics of the channel. Otherwise, returns NULL.
fetchBufferLength
- (unsigned)fetchBufferLength
Returns the size, in bytes, of the fetch buffer. The larger the buffer, the more rows can be returned for each round trip to the server.
See also: - setFetchBufferLength:
informixSetIsolationTo:
- (void)informixSetIsolationTo:
(InformixIsolationLevel)isolationLevel
Sets to isolationLevel the isolation transaction level of the connection represented by the receiver.
setFetchBufferLength:
- (void)setFetchBufferLength:
(unsigned)length
Sets to length the size, in bytes, of the fetch buffer. The larger the buffer, the more rows can be returned for each round trip to the server.
See also: - fetchBufferLength
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