OpenAccess SDK SQL Engine Core Functions API : Function Reference : dam_addLOBLocatorValToRow

dam_addLOBLocatorValToRow

This function gets LOB data from the IP, based on a request from the client. The IP calls this method to add the locator value. When a client requests data, OpenAccess SQL Engine invokes OAIP_GetLongData, which is then exported from the IP.

The IP layer can call this function to set a LOB locator value for the long data column specified by hCol in the row specified by hRow. Setting a LOB locator as the column value in the row allows the long data value for that column to be fetched in pieces. Fetching the long data in pieces can greatly reduce the amount of memory needed to process a query result because the entire long data value does not need to be held in memory.

The locator specified by pColVal is treated as an opaque handle. The SQL Engine does not process the locator. The SQL Engine passes the locator handle or object specified by pColVal to the OAIP_GetLongData function when it needs to fetch the actual data for the column.

To support streaming for a specific column, the IP should call this function to add a locator value. When the client requests data, the SQL Engine invokes OAIP_GetLongData, which must be exported from the IP.

The iXOType argument must be set to one of the following types:

for all columns:

XO_TYPE_DEFAULT

for LONGVARBINARY columns:

XO_TYPE_BINARY

XO_TYPE_VARBINARY

XO_TYPE_LONGVARBINARY

XO_TYPE_CHAR

XO_TYPE_VARCHAR

XO_TYPE_LONGVARCHAR

for LONGVARCHAR columns:

XO_TYPE_CHAR

XO_TYPE_VARCHAR

XO_TYPE_LONGVARCHAR

XO_TYPE_WCHAR

XO_TYPE_WVARCHAR

XO_TYPE_WLONGVARCHAR

int dam_addLOBLocatorValToRow(
DAM_HSTMT hstmt,
DAM_HROW hRow,
DAM_HCOL hCol,
int iXoType,
void * pColVal,
long lColValLen)

Table 57. Parameters for dam_addLOBLocatorValToRow
Parameter	Type	Description
IN
hstmt	DAM_HSTMT	The statement handle
hRow	DAM_HROW	The row handle
hCol	DAM_HCOL	The column handle
iXoType	int	Type of the stream.
pColVal	void *	LOB locator value, for example, File Handle.
IColValLen	long	The LOB locator value length.
RETURN
	int	DAM_SUCCESS - added the locator to the row. DAM_FAILURE - error adding the locator to the row.

dam_addLOBLocatorValToRow

See also