nsivarajan opened a new pull request, #65431:
URL: https://github.com/apache/doris/pull/65431
### What problem does this PR solve?
Issue Number: close #65422
Related PR: #xxx
**Problem Summary:**
Modern analytical workloads require querying data as it existed at a
specific point in time — for audit trails, data debugging, incremental pipeline
recovery, and regulatory compliance.
Apache Doris cloud/decoupled mode currently has no mechanism to read
historical versions of a table. Once data is compacted or overwritten, earlier
states are unrecoverable from SQL.
**Requested syntax:**
```sql
SELECT * FROM orders FOR TIME AS OF '2024-01-15 10:00:00';
CREATE TABLE snapshot AS
SELECT * FROM orders FOR TIME AS OF '2024-01-15 10:00:00';
```
Supported on all DML table models: Duplicate Key, Unique Key (MoW), and
Aggregate Key.
**Solution**
Key design points
Per-table opt-in — zero overhead for non-TT tables:
```sql
CREATE TABLE orders (...)
PROPERTIES (
"enable_time_travel" = "true",
"time_travel_retention_days" = "7"
);
```
**Two-level FDB index (cloud mode):**
Level 1: sparse version index — one FDB key per commit per partition (T → V
mapping)
Level 2: compaction checkpoint — pre-compaction rowset manifests written
before each cumulative compaction, so historical reads survive compaction
One batch RPC resolves all partitions and fetches all manifests in a single
FDB transaction — consistent snapshot across all partitions, one network round
trip.
Post-compaction correctness — the critical test: a query at timestamp T
returns identical results before and after compaction of the rowsets that
covered T.
**Scope**
Cloud/decoupled mode only (this PR)
Coupled/local storage mode: same architecture, separate follow-up (~40%
effort)
SHOW TIME TRAVEL ON : listed as future work
### Release note
None
### Check List (For Author)
- Test <!-- At least one of them must be included. -->
- [x] Regression test
- [x] Unit Test
- [ ] Manual test (add detailed scripts or steps below)
- [ ] No need to test or manual test. Explain why:
- [ ] This is a refactor/code format and no logic has been changed.
- [ ] Previous test can cover this change.
- [ ] No code files have been changed.
- [ ] Other reason <!-- Add your reason? -->
- Behavior changed:
- [ ] No.
- [x] Yes. <!-- Explain the behavior change -->
- Does this need documentation?
- [ ] No.
- [x] Yes. <!-- Add document PR link here. eg:
https://github.com/apache/doris-website/pull/1214 -->
### Check List (For Reviewer who merge this PR)
- [ ] Confirm the release note
- [ ] Confirm test cases
- [ ] Confirm document
- [ ] Add branch pick label <!-- Add branch pick label that this PR should
merge into -->
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