From 653729ce0ec1c38b444740637896d6ec706ef13a Mon Sep 17 00:00:00 2001 From: Andrew Dunstan Date: Fri, 3 Jan 2025 09:23:46 -0500 Subject: [PATCH] Document strange jsonb sort order for empty top level arrays Slightly faulty logic in the original jsonb code (commit d9134d0a355) results in an empty top level array sorting less than a json null. We can't change the sort order now since it would affect btree indexes over jsonb, so document the anomaly. Backpatch to all live branches (13 .. 17) In master, also add a code comment noting the anomaly. Reported-by: Yan Chengpen Reviewed-by: Jian He Discussion: https://postgr.es/m/OSBPR01MB45199DD8DA2D1CECD50518188E272@OSBPR01MB4519.jpnprd01.prod.outlook.com --- doc/src/sgml/json.sgml | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/doc/src/sgml/json.sgml b/doc/src/sgml/json.sgml index 3836bf5acf3..78b56f86907 100644 --- a/doc/src/sgml/json.sgml +++ b/doc/src/sgml/json.sgml @@ -584,12 +584,13 @@ SELECT jdoc->'guid', jdoc->'name' FROM api WHERE jdoc @@ '$.tags[*] == "qui"'; The btree ordering for jsonb datums is seldom of great interest, but for completeness it is: -Object > Array > Boolean > Number > String > Null +Object > Array > Boolean > Number > String > null Object with n pairs > object with n - 1 pairs Array with n elements > array with n - 1 elements + with the exception that (for historical reasons) an empty top level array sorts less than null. Objects with equal numbers of pairs are compared in the order: key-1, value-1, key-2 ...