Lightweight transactions¶

Use ScanCAS or MapScanCAS for a conditional statement. Always inspect the returned applied value:

var currentVersion int
applied, err := session.Query(
	"UPDATE documents SET body = ?, version = ? WHERE id = ? IF version = ?",
	newBody,
	nextVersion,
	documentID,
	expectedVersion,
).ScanCAS(&currentVersion)
if err != nil {
	return err
}
if !applied {
	// Another writer changed the document.
}

Use ExecuteBatchCAS or MapExecuteBatchCAS for conditional batches. At least one statement must be conditional. Every statement, including unconditional statements, must target the same table and partition, and every condition must succeed for the batch to apply.

Both methods return an iterator after scanning the first result row. Always close a non-nil iterator, even when no additional rows are needed, and handle the error from Iter.Close so its page buffers and other resources are released.

Lightweight transactions use Paxos and cost more than ordinary reads and writes. Use them only when compare-and-set semantics are required.