JSONB Tricks: Operators, Indexes, and When to (Not) Use It | PostgresOpen 2019 | Colton Shepard

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September 12, 2019

JSONB Tricks: Operators, Indexes, and When to (Not) Use It | PostgresOpen 2019 | Colton Shepard

When do you use jsonb, and when don’t you? How do you make it fast? What operators are available, and what can they do? How will this change? These are all very good questions, but jsonb support in Postgres moves so fast that it’s hard to keep up.

In this talk, you will get details on these topics, complete with practical examples and real-world stories:

When to use jsonb, what it’s good for, and when to not use it
- Operators and how to use them effectively
- Indexing, operator support for indexes, and the tradeoffs involved
- Postgres 12 improvements and new features

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Citus Data

September 12, 2019
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Transcript

  1. Colton Shepard PostgresOpen 2019

  2. What is all this, anyways? JavaScript Object Notation Data Interchange

    Format RFC 7158 Human readable lightweight data format One of 2 Postgres JSON data types. Decomposed for storage, not stored as string • Fast and indexable • High disk usage
  3. Good use cases Entity–attribute–value model tables

  4. Customer Story!

  5. Less Good Use Cases: Statistics Gathering Issues

  6. Other Less Good Use Cases

  7. Customer Story: Heap Analytics https://heap.io/blog/engineering/when-to-avoid-jsonb-in-a-postgresql-schema

  8. Customer Story: Anonymous, Inc.

  9. Operators

  10. -> and ->>

  11. The ? operator Does this string exist as a top-level

    key within the JSON value?
  12. The ? operator What about this array of strings?

  13. The ? operator

  14. The @ operator

  15. #> and #>>

  16. Operator-friendly indexes

  17. B-Tree

  18. B-Tree Function Index

  19. Hash

  20. Hash function indexes

  21. GiST, SP-GiST, and BRIN

  22. GIN This

  23. GIN with jsonb_path_ops

  24. GIN with jsonb_ops (default)

  25. Special mention: GIN function index with gin_trgm_ops

  26. Postgres 12 New datatype: jsonpath Provides a binary representation of

    the parsed SQL/JSON path expression 1. .key returns object member with specified key 2. .* returns all object members at current level 3. .** returns all object members at current level and below 4. .**{level} or .**{start_level to end_level} returns all at specified level(s) 5. [subscript, ...] returns the value at specified array location https://www.postgresql.org/docs/devel/datatype-json.html#DATATYPE-JSONPATH
  27. Postgres 12: The jsonb_path_query operator

  28. Postgres 12: jsonb_path_query with .* and .**

  29. Postgres 12: jsonb_path_query with .**{level}

  30. Postgres 12: jsonb_path_query with arrays

  31. Postgres 12: the jsonb_path_exists operator Gives bool indicating whether the

    path exists.
  32. Postgres 12: the jsonb_path_match operator This allows for any logic

    that’ll output Boolean results
  33. Postgres 12: the jsonb_path_query_array operator Much like jsonb_path_query, but you

    get an array instead:
  34. Postgres 12: the jsonb_path_query_first operator Get first matching result:

  35. Conclusion

  36. General resources to learn more https://www.youtube.com/watch?v=AeMaBwd90SI https://heap.io/blog/engineering/when-to-avoid-jsonb-in-a- postgresql-schema https://bitnine.net/blog-postgresql/postgresql-internals-jsonb- type-and-its-indexes/

    https://www.citusdata.com/blog/2016/07/14/choosing-nosql- hstore-json-jsonb/ https://www.postgresql.org/docs/12/functions- json.html#FUNCTIONS-SQLJSON-PATH https://paquier.xyz/postgresql-2/postgres-12-jsonpath/ https://www.citusdata.com/blog/2016/07/25/sharding-json-in- postgres-and-performance/
  37. @Azure Database for MySQL, PostgreSQL & MariaDB