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This function can replace two calls to the server with one, reducing traffic and boosting performance.
Declaration
NINT ctSetAutoContextId(COUNT contextId);
Description
To use ctSetAutoContextId() as a replacement for ChangeISAMContext() at the ISAM level, call ctSetAutoContextId(), passing the context ID you wish to use in the next record read call. Check for a return code of NO_ERROR to indicate success. Then call your record read function. The following functions are the record read functions that support this feature:
BLKIREC, EQLVREC, EQLREC, GTEVREC, GTEREC, GTVREC, GTREC, GetLTEVRecord, LTEREC, LTVREC, LTREC
Example
FILNO datno1,datno2; /* data file numbers */
pVOID bufptr1,bufptr2; /* data buffer pointer */
COUNT contextID_1,contextID_2,contextID_3; /* context ID's */
OpenFileWithResource(datno1,"data1",ctSHARED);
OpenFileWithResource(datno2,"data2",ctSHARED);
/* move to first record for datno1 using first key */
FirstRecord(datno1 + 1,bufptr1);
/* establish first context for datno1 at first record. keyno == -1 saves all key positions. */
contextID_1 = OpenISAMContext(datno1,-1,-1);
/* move to first record for datno2 using third key. */
FirstRecord(datno2 + 3,bufptr2);
/* establish first context for datno2 at first record. keyno != -1 saves only key value for third key. */
contextID_2 = OpenISAMContext(datno2, datno2 + 3,-1);
NextRecord(datno1 + 1,bufptr1);
/* position datno1 at third record by first key. */
NextRecord(datno1 + 1,bufptr1);
/* Third record by first key becomes the saved position for contextID_1 and contextID_3 becomes the active context for datno1. */
contextID_3 = OpenISAMContext(datno1,-1,-1);
/* move from third record by first key, to the next record using the second key. Call this record 4' */
NextRecord(datno1 + 2,bufptr1);
/* Save record 4' as contextID_3. Make the 3rd record the current position for datno1, and contextID_1 becomes the active context for datno1. contextID_2 is still the active context for datno2. */
ctSetAutoContextId(contextID_1);
/* move to the 4th record by key 1 for datno1.*/
NextRecord(datno1 + 1,bufptr1);
