Lesson plan

Partial index

In databases, a partial index, also known as filtered index, is an index which has some condition applied to it so that it includes a subset of rows in the table. This allows the index to remain small, even though the table may be rather large, and have extreme selectivity. Suppose you have a transaction table where entries start out with STATUS = 'A' (active), and then may pass through other statuses ('P' for pending, 'W' for "being worked on") before reaching a final status, 'F', at which point it is no longer likely to be processed again. In PostgreSQL, a useful partial index might be defined as: create index partial_status on txn_table (status) where status in ('A', 'P', 'W'); This index would not bother storing any of the millions of rows that have reached "final" status, 'F', and would allow queries looking for transactions that still "need work" to efficiently search via this index. Similarly, a partial index can be used to index only those rows where a column is not null, which will be of benefit when the column usually is null.…

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Article summary

In databases, a partial index, also known as filtered index, is an index which has some condition applied to it so that it includes a subset of rows in the table. This allows the index to remain small, even though the table may be rather large, and have extreme selectivity. Suppose you have a transaction table where entries start out with STATUS = 'A' (active), and then may pass through other statuses ('P' for pending, 'W' for "being worked on") before reaching a final status, 'F', at which point it is no longer likely to be processed again. In PostgreSQL, a useful partial index might be defined as: create index partial_status on txn_table (status) where status in ('A', 'P', 'W'); This index would not bother storing any of the millions of rows that have reached "final" status, 'F', and would allow queries looking for transactions that still "need work" to efficiently search via this index. Similarly, a partial index can be used to index only those rows where a column is not null, which will be of benefit when the column usually is null.…

Key claims

  1. release date: 2002 — source: Wikipedia · confidence 0.95

Discussion questions

  1. Summarise the article in your own words. Which single claim would you verify first, and why?
  2. The record states that the release date is "2002". What evidence would count against this claim?
  3. Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
  4. If two sources disagreed about one of these facts, what would you need in order to trust one over the other?

Bibliography

  1. Wikipedia https://en.wikipedia.org/w/index.php?oldid=1370514467

Key claims and bibliography are generated from the same tracked claims and sources as the article page.