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EdmiError edmiDefinePersistentAttrHashTableBN(SdaiString schemaName,
SdaiString entityName,
SdaiString attributeName,
SdaiOptions options,
SdaiInteger hashTableWidth,
SdaiInteger attrStringLength);
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To increase search speed in the database, it is possible to define persistent hash tables. A hash table is a persistent data structure in the database that speeds up the search for instances of one entity in one schema via the value of one attribute. The hash table is created when a data model of the specified schema is created and it is maintained during the entire lifetime of the model or until it is deleted. If there exist a data model based on the specified schema when the hash table is defined, this model do not get a hash table. In this case the model must be exported to a STEP file, deleted and recreated from the STEP file. Likewise is not an attribute hash table of data model removed if the attribute hash table definition is removed from the underlying schema of the data model.
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This function defines attribute hash table connected to the specified attribute in the specified schema.
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The search in hash tables is done explicitly by the following edmi functions: edmiRemoteGetHashedAttrInstance, edmiRemoteGetHashedAttrInstanceBN, edmiRemoteGetHashedAttrInstances, edmiRemoteGetHashedAttrInstancesBN, edmiGetHashedAttrInstance, edmiGetHashedAttrInstanceBN, edmiGetHashedAttrInstances and edmiGetHashedAttrInstancesBN
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Arguments
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| Type | Name | Comment |
| SdaiString | schemaName | Specifies the name of EXPRESS schema to which the persistent attribute hash table is to be defined. This EXPRESS schema must exist as a dictionary model in the EDMdatabase. Schema names are case insensitive. Schema names are unique in an EDMdatabase. |
| SdaiString | entityName | Specifies the name of an entity in the schema <schemaName>. in which the persistent attribute hash table is to be defined. Entity names are case insensitive. |
| SdaiString | attributeName | Name of the attribute to which the persistent attribute hash table is to be defined. |
| SdaiOptions | options | A The <options> value should be specified as a bitwise OR between the options to enable. All options name are defined in the header file sdai.h . |
| SdaiInteger | hashTableWidth | OptionalNumber of hash table entries. Future extension: in bytes. |
| SdaiInteger | attrStringLength | Optional. String length for [ FIXED_STRING_LENGTH]. |
Option Description
MULTIPLE_ATTRIBUTES | Only for EDM internal usage |
MULTIPLE_ENTITIES | Only for EDM internal usage |
ALL_ATTR_OCCURENCES | Only for EDM internal usage |
Return Value
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Options
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| Option | Comment |
DELETE_ATTRIBUTE_HASH_TABLE | If this option is used, the The existing hash table of the specified attribute is deleted. No new hash table is defined. |
REDEFINE_ATTRIBUTE_HASH_TABLE | If this option is used, the The existing hash table of the specified attribute is deleted and a new hash table is defined. |
SUBTYPES | Specifies that in addition to all instances of the type specified by the <entityName> <entityId> argument, all subtype instances of the specified type should be queried as well. |
FIXED_STRING_LENGTH | If this option is used, the argument "Attribute The argument <Attribute (fixed) string length" length> is taken as the fixed string length of the attribute. |
UNIQUE_ATTRIBUTE_VALUES | If this option is used it is checked EDM checks that the attribute is unique when a new instance is stored or an attribute is modified. |
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Example
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See also
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