c-treeDB API for C++ - Developers Guide

CTDB_ON_TABLE_GET_SCHEMA

A CTDB_ON_TABLE_GET_SCHEMA callback is invoked after the FairCom DB data and index files are open and the CTDB_ON_TABLE_OPEN callback is invoked. This callback is also invoked after the FairCom DB data file record schema object is loaded into the table handle.

You may use the CTDB_ON_TABLE_GET_SCHEMA callback event to modify FairCom DB schema information stored in the table handle. You should typecast the table handle to a pCTDBTABLE structure pointer. The following CTDBTABLE structure members keep schema information:

CTDBTABLE Structure Member	Explanation
pConvMap schemaptr	c-tree ConvMap structure pointer
VRLEN schema_size	size in bytes of allocated ConvMap structure

At the point a CTDB_ON_TABLE_GET_SCHEMA callback is invoked, the table’s schema has already been loaded and stored in the schemaptr member of CTDBTABLE structure. The schema_size member contains the allocated size of schemaptr.

c-treeDB C API Example

CTDBRET ctdbDECL OnTableGetSchema(CTHANDLE Handle)

{

CTDBRET Retval = CTDBRET_OK;

pCTDBTABLE pTable = (pCTDBTABLE)Handle;

if (!pTable)

Retval = CTDBRET_NOTTABLE;

else

{

/* change the field padding byte */

if (pTable->schemaptr)

pTable->schemaptr->padding = ' ';

}

return Retval;

}