To confirm that we have not lost any data we can perform an as of query We want to query the state of the blueprint at time 3 before the non destructive update We from We created a blueprint with key at time 3 and edited it at time 4 We can query as of any time in the range We ll use the beginning of the range Plugging these values into the template we GET The response we get from is nearly identical to the response we would have got from had we run the query at time 3 This makes sense There s a small difference in the data Some of the values that used to be are now time 4 This illustrates an important rule of temporal data All writes into the data store are immutable and append only except for the value Next we ll focus on the data store In this example we re using a relational database but these concepts apply to any data store The schema maps closely to the json examples above so if you re comfortable with the data feel free to skip ahead to the queries BLUEPRINT after create systemFrom systemTo key blueprint title descriptionMarkdown imgurImageId blueprintStringSha 2001 01 03 23 59 59 0 9999 12 01 23 59 00 0 6ed1 Blueprint title Blueprint description markdown Imgur ID 1 cc34 BLUEPRINT after update systemFrom systemTo key blueprint title descriptionMarkdown imgurImageId blueprintStringSha ` icon minus stroke red ` 2001 01 03 23 59 59 0 ` icon plus stroke green ` 2001 01 04 23 59 59 0 6ed1 ` icon minus stroke red ` Blueprint title ` icon minus stroke red ` Blueprint description markdown Imgur ID 1 cc34 ` icon plus stroke green ` 2001 01 04 23 59 59 0 9999 12 01 23 59 00 0 6ed1 ` icon plus stroke green ` Edited blueprint title ` icon plus stroke green ` Edited Blueprint description markdown Imgur ID 1 cc34 BLUEPRINT_VERSION after create systemFrom systemTo key createdById lastUpdatedById number createdOn 2001 01 03 23 59 59 0 9999 12 01 23 59 00 0 6ed1 User ID User ID 1 2001 01 03 23 59 59 0 BLUEPRINT_VERSION after update systemFrom systemTo key createdById lastUpdatedById number createdOn ` icon minus stroke red ` 2001 01 03 23 59 59 0 ` icon plus stroke green ` 2001 01 04 23 59 59 0 6ed1 User ID User ID ` icon minus stroke red ` 1 2001 01 03 23 59 59 0 ` icon plus stroke green ` 2001 01 04 23 59 59 0 9999 12 01 23 59 00 0 6ed1 User ID User ID ` icon plus stroke green ` 2 2001 01 03 23 59 59 0 Temporal Schema patterns All tables have and columns Old data is phased out by setting to now New data is phased in by setting to now The new row s and the old row s are set to the same value forming a contiguous timeline When several tables are edited within a transaction the and values are set to the same value across all tables Unchanged data is copied from the old row to the new row For very wide columns that don t change frequently it may be more efficient to split out a separate table The value of the new row is set to to indicate that the row is still active In json we had used to represent the infinity date 2001 01 03 GET api blueprint blueprintKey asOf asOf 6ed1f638 a63c 3a54 af67 ba494f27bff2 2001 01 03 2001 01 04 2001 01 03 2001 01 04 2001 01 03 api blueprint 6ed1f638 a63c 3a54 af67 ba494f27bff2 asOf 2001 01 03T23 59 59Z key 6ed1f638 a63c 3a54 af67 ba494f27bff2 systemFrom 2001 01 03T23 59 59Z systemTo null systemTo 2001 01 04T23 59 59Z version number 1 systemFrom 2001 01 03T23 59 59Z systemTo null systemTo 2001 01 04T23 59 59Z createdOn 2001 01 03T23 59 59Z createdBy userId User ID lastUpdatedBy userId User ID title Blueprint title voteSummary numberOfUpvotes 0 systemFrom 2001 01 03T23 59 59Z systemTo null blueprintString sha cc341849b4086ce7b1893b366b0dc8e99ce4e595 createdOn 2001 01 02T23 59 59Z createdBy userId User ID imgurImage imgurId Imgur ID 1 imgurType image png height 300 width 300 systemFrom 2001 01 01T23 59 59Z systemTo null descriptionMarkdown Blueprint description markdown tags tagCategory belt tagName balancer systemFrom 2001 01 03T23 59 59Z systemTo null tag category belt name balancer ordinal 1 systemFrom 2000 01 01T00 00 00Z systemTo null api blueprint blueprintKey asOf 2001 01 03T23 59 59Z api blueprint blueprintKey 2001 01 03 systemTo null 2001 01 04 systemTo systemFrom systemTo systemTo systemFrom systemFrom systemTo systemFrom systemTo systemTo 9999 12 01 23 59 00 00 null

As of queries are implemented in SQL by adding temporal criteria to our clause Now we can see why the infinity date is represented as If we instead used we d need to add additional criteria to our WHERE clauses Joins that are one hop away from our main table are similar Joins that are two hops away from our main table are more complicated We ll see examples of these later Temporal query patterns We perform asOf queries by adding to our clause We add this exact came criteria to every query We always all columns from the table In the examples above we used In production usage it s common to list the columns explicitly We never columns from two tables in the same query Even in the upcoming examples of joins we always from one table at a time In the next section we ll learn about adding versions and querying as of a version number WHERE select * from BLUEPRINT t0 where t0 key 6ed1f638 a63c 3a54 af67 ba494f27bff2 and t0 system_from < 2001 01 03 23 59 59 000 and t0 system_to > 2001 01 03 23 59 59 000 9999 12 01 23 59 00 00 null select * from BLUEPRINT_TAG t0 where t0 blueprint_key 6ed1f638 a63c 3a54 af67 ba494f27bff2 and t0 system_from < 2001 01 03 23 59 59 000 and t0 system_to > 2001 01 03 23 59 59 000 where system_from < asOf and system_to > asOf WHERE SELECT SELECT * SELECT SELECT