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Reference/es_mbc_addfldidx
Syntax
int es_mbc_addfldidx( struct es_mbc *cls, const char *fldnm );
Arguments
struct es_mbc *cls |
A database class. |
|---|---|
const char *fieldnm |
Field name. |
Return Codes
ES_ERROR_NONE |
Success. No errors. | |
|---|---|---|
ES_ERROR_INVALIDINDEX |
Cannot add index fields to a subclass if the super class has a shared index (ES_INDEX_SHARED). | |
ES_ERROR_INDEXDEFINED |
Cannot add more than one field to a None index (ES_INDEX_NONE). |
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ES_ERROR_UNKNOWNFIELD |
Field has not been added to class. | |
ES_ERROR_INVALIDINDEXTYPE |
Field is not of an integer type. |
Description
Add a field to the index definition of a class. The set of all index fields must constitute a unique key for the class, unless the class is designated as ES_INDEX_NONE and has been assigned no index fields.
The index of a class is defined when the class is created, via a call to es_mbc_new. Depending on the type of the index, one or more fields may be added to the index definition via es_mbc_addfldidx. The field must first be defined and added to the class via es_mbc_addfld.
Only integer fields (i.e. 8,16,32 or 64bit integers) may form part of an index.
The order in which es_mbc_addfld() is invoked determines the ordering of fields in an index. This can impact the performance of look-up operations as described in the Index Types section.
/* construct root class "Sales" and add three database field definitions */ struct es_mbc *c_sales; es_mbc_new( schema, "Sales", 4096, ES_INDEX_PRIVATE, NULL, &c_sales ); es_mbc_addfld( c_sales, "ProductId", ES_FLDTYPE_I16 ); es_mbc_addfld( c_sales, "CustomerId", ES_FLDTYPE_I32 ); es_mbc_addfld( c_sales, "UnitSales", ES_FLDTYPE_F64 ); /* define ProductId and CustomerId to be the key */ es_mbc_addfldidx( c_sales, "ProductId" ); es_mbc_addfldidx( c_sales, "CustomerId" );