CAP: 0017
Title: Update LastModifiedLedgerSeq If and Only If LedgerEntry is Modified
Author: Jonathan Jove
Status: Accepted
Created: 2019-02-01
Discussion: https://groups.google.com/forum/#!topic/stellar-dev/hzemjh1aIwc
Protocol version: TBD
This proposal makes specifying and implementing the protocol easier by simplifying the semantics of
LedgerEntry.lastModifiedLedgerSeq.
It is currently possible for LedgerEntry.lastModifiedLedgerSeq to be updated by an operation even
if that operation did not make any modifications to the underlying data of that LedgerEntry. This
document proposes changing the semantics of lastModifiedLedgerSeq to be updated by an operation
if and only if the underlying data of that LedgerEntry has changed.
The main benefit of this proposal is that implementing the protocol would be simpler. The current
behavior forces implementers to carefully manage whether lastModifiedLedgerSeq should or should
not be updated in any given circumstance. The only reliable way for an implementer to determine
when lastModifiedLedgerSeq should be updated in the current protocol version is by referring to
an existing implementation. This proposal would unambiguously specify when lastModifiedLedgerSeq
should and should not be updated.
For example, using AllowTrust to authorize a trustline that is already authorized will update the
lastModifiedLedgerSeq of the trustline without making any other modifications. In contrast, a
tentative winner of Inflation that ends up winning nothing (due to, for example, having excessive
native asset liabilities) is unchanged and does not receive an updated lastModifiedLedgerSeq.
The value of lastModifiedLedgerSeq should be updated by an operation if and only if the net
effect of that operation includes updating the underlying data of a LedgerEntry. Specifically, if
leBefore and leAfter are the LedgerEntry (excluding lastModifiedLedgerSeq) before and after
the operation has been applied, respectively, then lastModifiedLedgerSeq should be updated to
LedgerHeader.ledgerSeq if and only if leBefore != leAfter.
This proposal is to be applied at the operation level as it guarantees that if the net effect of
any operation in a transaction set includes updating the underlying data of a LedgerEntry then
the value of lastModifiedLedgerSeq will be updated. This behavior is desirable from an
implementation perspective because it allows each operation to correctly determine whether
lastModifiedLedgerSeq should be updated without any knowledge of whether the LedgerEntry has
been or will be modified by other operations in the same transaction set.
Downstream systems which rely on lastModifiedLedgerSeq could be effected as the semantics of that
field will change.
None yet.
No implementation yet.