1. APIs and Business Functions Guide
  2. Setting Up Indexes

Setting Up Indexes

To store or retrieve any data in JDECACHE, you must set up at least one index that consists of at least one column. The index is limited to a maximum of 25 columns (which are called segments) in the index structure. Use the data type provided to tell the cache manager what the index looks like. You must provide the number of columns (segments) in the index and the offset and size of each column in the data structure. To maximize performance, minimize the number of segments.

This code is the definition of the structure that holds index information:

#define JDECM_MAX_UM_SEGMENTS 25
struct _JDECMKeySegment
{
 short int nOffset;  /* Offset from beginning of structure in bytes */
 short int nSize;  /* Size of data item in bytes */
 int idDataType;  /* EVDT_MATH_NUMERIC or EVDT_STRING*/
} JDECMKEYSEGMENT;
struct _JDECMKeyStruct
{
 short int nNumSegments;
 JDECMKEYSEGMENT CacheKey[JDECM_MAX_NUM_SEGMENTS];
} JDECMINDEXSTRUCT;

Observe these rules when you create indices in JDECACHE:

  • Always declare the index structure as an array that holds one element for single indexes.

    Declare the index structure as an array that holds more than one element for multiple indexes. You can create an unlimited number of indexes.

  • Always use memset() for the index structure.

    When you use memset() for multiple indexes, multiply the size of the index structure by the total number of indexes.

  • Always assign as elements the number of segments that correspond to the number of columns that you have in the CacheKey array.

  • Always use offsetof () to indicate the offset of a column in the structure that contains the columns.

This example illustrates a single index with multiple fields:

/* Example of single index with multiple fields.*/
JDECMINDEXSTRUCT Index[1]    = {0};
memset(&dsCache,0x00,sizeof(dsCache));
/* Initialize cache. */
Index->nNumSegments=5;
Index->CacheKey[0].nOffset=offsetof(DSCACHE,szEdiUserId);
Index->CacheKey[0].nSize=DIM(dsCache.szEdiUserId);
Index->CacheKey[0].idDataType=EVDT_STRING;
Index->CacheKey[1].nOffset=offsetof(DSCACHE,szEdiBatchNumber);
Index->CacheKey[1].nSize=DIM(dsCache.szEdiBatchNumber);
Index->CacheKey[1].idDataType=EVDT_STRING;
Index->CacheKey[2].nOffset=offsetof(DSCACHE,szEdiTransactNumber);
Index->CacheKey[2].nSize=DIM(dsCache.szEdiTransactNumber);
Index->CacheKey[2].idDataType=EVDT_STRING;
Index->CacheKey[3].nOffset=offsetof(DSCACHE,mnEdiLineNumber);
Index->CacheKey[3].nSize=sizeof(dsCache.mnEdiLineNumber);
Index->CacheKey[3].idDataType=EVDT_MATH_NUMERIC;
Index->CacheKey[4].nOffset=offsetof(DSCACHE.cErrorCode);
Index->CacheKey[4].nSize = 1;
Index->CacheKey[4].idDataType=EVDT_CHAR

The flag, idDataType, indicates the data type of the particular key.

This example illustrates a cache with multiple indices and multiple fields:

Memset(jdecmIndex,0x00,sizeof(JDECMINDEXSTRUCT)*2);
jdecmIndex[0].nKeyID=1;
jdecmIndex[0].nNumSegments=6;
jdecmIndex[0].CacheKey[0].nOffset=offsetof(I1000042,szCostCenter);
jdecmIndex[0].CacheKey[0].nSize=DIM(dsI1000042.szCostCenter);
jdecmIndex[0].CacheKey[0].idDataType=EVDT_STRING;
jdecmIndex[0].CacheKey[1].nOffset=offsetof(I1000042,szObjectAccount);
jdecmIndex[0].CacheKey[1].nSize=DIM(dsI1000042.szObjectAccount);
jdecmIndex[0].CacheKey[1].idDataType=EVDT_STRING;
jdecmIndex[0].CacheKey[2].nOffset=offsetof(I1000042,szSubsidiary);
jdecmIndex[0].CacheKey[2].nSize=DIM(dsI1000042.szSubsidiary);
jdecmIndex[0].CacheKey[2].idDataType=EVDT_STRING;
jdecmIndex[0].CacheKey[3].nOffset=offsetof(I1000042,szSubledger);
jdecmIndex[0].CacheKey[3].nSize=DIM(dsI1000042.szSubledger);
jdecmIndex[0].CacheKey[3].idDataType=EVDT_STRING;
jdecmIndex[0].CacheKey[4].nOffset=offsetof(I1000042,szSubledgerType);
jdecmIndex[0].CacheKey[4].nSize=1;
jdecmIndex[0].CacheKey[4].idDataType=EVDT_STRING;
jdecmIndex[0].CacheKey[5].nOffset=offsetof(I1000042,szCurrencyCodeFrom);
jdecmIndex[0].CacheKey[5].nSize=DIM(dsI1000042.szCurrencyCodeFrom);
jdecmIndex[0].CacheKey[5].idDataType=EVDT_STRING;
************************ KEY 2 *******************************
jdecmIndex[1].nKeyID=2;
jdecmIndex[1].nNumSegments=7;
jdecmIndex[1].CacheKey[0].nOffset=offsetof(I1000042,szEliminationGroup);
jdecmIndex[1].CacheKey[0].nSize=DIM(dsI1000042.szEliminationGroup);
jdecmIndex[1].CacheKey[0].idDataType=EVDT_STRING;
jdecmIndex[1].CacheKey[1].nOffset=offsetof(I1000042,szCostCenter);
jdecmIndex[1].CacheKey[1].nSize=DIM(dsI1000042.szCostCenter);
jdecmIndex[1].CacheKey[1].idDataType=EVDT_STRING;
jdecmIndex[1].CacheKey[2].nOffset=offsetof(I1000042,szObjectAccout);
jdecmIndex[1].CacheKey[2].nSize=DIM(dsI1000042.szObjectAccount);
jdecmIndex[0].CacheKey[2].idDataType=EVDT_STRING;
jdecmIndex[1].CacheKey[3].nOffset=offsetof(I1000042,szSubsidiary);
jdecmIndex[1].CacheKey[3].nSize=DIM(dsI1000042.szSubsidiary);
jdecmIndex[1].CacheKey[3].idDataType=EVDT_STRING;
jdecmIndex[1].CacheKey[4].nOffset=offsetof(I1000042,szSubledger);
jdecmIndex[1].CacheKey[4].nSize=DIM(dsI1000042.szSubledger);
jdecmIndex[1].CacheKey[4].idDataType=EVDT_STRING;
jdecmIndex[1].CacheKey[5].nOffset=offsetof(I1000042,szSubledgerType);
jdecmIndex[1].CacheKey[5].nSize=1;
jdecmIndex[1].CacheKey[5].idDataType=EVDT_STRING;
jdecmIndex[1].CacheKey[6].nOffset=offsetof(I1000042,szCurrencyCodeFrom);
jdecmIndex[0].CacheKey[6].nSize=DIM(dsI1000042.szCurrencyCodeFrom);
jdecmIndex[0].CacheKey[6].idDataType=EVDT_STRING;