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Compare Exchange: How to Delete Compare Exchange Value
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Use
DeleteCompareExchangeValueOperationto delete a Key and its Value. -
The Key and its Value are deleted only if the index in the request matches the current index stored in the server for the specified key.
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For an overview of the 'Compare Exchange' feature click: Compare Exchange Overview
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In this page:
Syntax
Method:
public DeleteCompareExchangeValueOperation(Class<T> clazz, String key, long index)| Parameters | ||
|---|---|---|
| key | String | The key to be deleted |
| index | long | The version number of the value to be deleted |
Returned object:
public class CompareExchangeResult<T> {
private T value;
private long index;
private boolean successful;
public T getValue() {
return value;
}
public void setValue(T value) {
this.value = value;
}
public long getIndex() {
return index;
}
public void setIndex(long index) {
this.index = index;
}
public boolean isSuccessful() {
return successful;
}
public void setSuccessful(boolean successful) {
this.successful = successful;
}
}| Return Value | |||
|---|---|---|---|
| Successful | boolean | * True if the delete operation was successfully completed * True if key doesn't exist * False if the delete operation failed |
|
| Value | T |
* The value that was deleted upon a successful delete * 'null' if key doesn't exist * The currently existing value on the server if delete operation failed |
|
| Index | long | * The next available version number upon success * The next available version number if key doesn't exist * The currently existing index on the server if the delete operation failed |
Example
// First, get existing value
CompareExchangeValue<User> readResult
= store.operations().send(
new GetCompareExchangeValueOperation<>(User.class, "AdminUser"));
// Delete the key - use the index received from the 'Get' operation
CompareExchangeResult<User> deleteResult
= store.operations().send(
new DeleteCompareExchangeValueOperation<>(User.class, "AdminUser", readResult.getIndex()));
// The delete result is successful only if the index has not changed between the read and delete operations
boolean deleteResultSuccessful = deleteResult.isSuccessful();
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