postgis-workshop/history_tracking — Chinese (Simplified) @ OSGeo Weblate: See Also

Zen

	English	Chinese (Simplified)	Actions
	For an insert, we just add a new record into the history table with the creation time/user.
	For a deletion, we just mark the currently active history record (the one with a NULL deletion time) as deleted.
	For an update, we first mark the active history record as deleted, then insert a new record for the updated state.
	Editing the Table
	Now that the history table is enabled, we can make edits on the main table and watch the log entries appear in the history table.
	Note the power of this database-backed approach to history: no matter what tool is used to make the edits, whether the SQL command line, a web-based JDBC tool, or a desktop tool like QGIS, the history is consistently tracked.
	SQL Edits
	Let's turn the two streets named "Cumberland Walk" to the more stylish "Cumberland Wynde":
	Updating the two streets will cause the original streets to be marked as deleted in the history table, with a deletion time of now, and two new streets with the new name added, with an addition time of now. You can inspect the historical records:
	Querying the History Table
	Now that we have a history table, what use is it? It's useful for time travel! To travel to a particular time T, you need to construct a query that includes:
	All records created before T, and not yet deleted; and also
	All records created before T, but deleted after T.
	We can use this logic to create a query, or a view, of the state of the data in the past. Since presumably all your test edits have happened in the past couple minutes, let's create a view of the history table that shows the state of the table 10 minutes ago, before you started editing (so, the original data).
	We can also create views that show just what a particular used has added, for example:
	See Also	或者你看看
	`QGIS open source GIS <http://qgis.org>`_
	`PostgreSQL Triggers <http://www.postgresql.org/docs/current/static/plpgsql-trigger.html>`_
	`PostgreSQL Range Types <https://www.postgresql.org/docs/current/rangetypes.html>`_

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