Delete
function Delete(const aInValue: string): Boolean;
Example
procedure ScriptEvent(var Value: Variant);
var TestMap: TvxMappingItem;
begin
// Run only in a governed non-production configuration task.
TestMap := Mappings['DOC_EXAMPLE_STATUS'];
Value := TestMap.Delete('ObsoleteCode');
end;
Usage
Deletes mapping-data rows for one input value while retaining the mapping definition and reporting no-op deletion as success.
Parameter
aInValue is matched against [Mapping_Data].[InValue] using the system database's collation. Velox quotes it with SafeSQL, removing NUL characters and doubling apostrophes.
Returns
The result starts as True. It remains True when MapNum is zero, when no row matches, or when the delete statement succeeds. It becomes False only when a caught database exception occurs. The method does not inspect affected-row count.
Additional Technical Info
Delete removes all [Mapping_Data] rows matching this item's numeric mapping identity and the supplied input value.
Behaviour and side effects
When MapNum is nonzero, the method synchronously executes:
DELETE FROM [Mapping_Data]
WHERE MappingNum = <current MapNum> AND InValue = <quoted input>
The mapping definition in [Mapping], cached Code/metadata and other inputs are unchanged. A later GetOutValue for the deleted input normally returns an empty string.
Edge cases and quirks
- A zero MapNum is a silent no-op success; Delete does not create or validate a map.
- A nonzero but stale MapNum can also return True while deleting nothing.
- Database collation determines case and accent sensitivity, so the matched input may not be byte-for-byte identical to the argument.
- There is no item/list lock. Lookup/Add/Delete operations from other threads can interleave; a row can be recreated immediately after deletion.
- Database exceptions are logged with the misleading text "error creating Mapping_Data table entry", then swallowed and returned as False.
- This permanently changes shared configuration data. Do not call it in normal record processing or use a True result as evidence that a row previously existed.
Delete does not invalidate the process-global mapping item because value pairs are queried live rather than cached. Use TvxMappingList.RemoveMap only when definition metadata itself must be reloaded.