Write timestamp

As explained in ScyllaDB in Action

A write timestamp is the timestamp attached to a database write for ordering concurrent updates.

A write timestamp is attached to each ScyllaDB write and helps reconcile concurrent updates. When values conflict, the higher timestamp wins, so the newer value overwrites the older one. Inspect a column’s timestamp with WRITETIME or override it with a USING TIMESTAMP clause. section 6.6

Protecting data during migration

Suppose a migrator reads an article while an editor updates it through a dual-write workflow. If the migrator inserts its older copy with a higher timestamp, ScyllaDB can treat that copy as newer and overwrite the editor’s change. Use USING TIMESTAMP with a value no later than the start of the migrator’s read queries, preferably preserving the source database’s timestamp. section 12.2.4

Figure 12.7 If a dual-write updates a value that your migration has recently read but not updated, you can overwrite newer versions of data in your source application.

Trace how a dual-write update can race with a migrator and cause a higher-timestamp migration write to replace newer application data. section 12.2.4

How ScyllaDB in Action covers it

How deep it goes

Explains last-write-wins, WRITETIME, and USING TIMESTAMP, then applies ordering rules to a dual-write migration race.

Examples

Uses concurrent article edits and a migrator inserting a recently read copy as the central conflict example.

What you can do after

Operate/configure migrations with USING TIMESTAMP to reduce the risk of overwriting concurrent updates.

How it connects

Connects write timestamps to concurrent updates, last-write-wins, dual writes, and data migration.

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Related concepts

• USING TIMESTAMP clauseconfigured by · The USING TIMESTAMP clause is a CQL write clause that specifies the timestamp assigned to an operation.
• last-write-winsuses · Last-write-wins is a conflict-resolution strategy that selects the update ordered latest among conflicting updates.

This explainer was generated by Manning's knowledge graph from the text of ScyllaDB in Action. The section links point to the parts of the book it draws on.