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JSON_TABLE: Add support for NESTED paths and columns

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A NESTED path allows to extract data from nested levels of JSON
objects given by the parent path expression, which are projected as
columns specified using a nested COLUMNS clause, just like the parent
COLUMNS clause.  Rows comprised from a NESTED columns are "joined"
to the row comprised from the parent columns.  If a particular NESTED
path evaluates to 0 rows, then the nested COLUMNS will emit NULLs,
making it an OUTER join.

NESTED columns themselves may include NESTED paths to allow
extracting data from arbitrary nesting levels, which are likewise
joined against the rows at the parent level.

Multiple NESTED paths at a given level are called "sibling" paths
and their rows are combined by UNIONing them, that is, after being
joined against the parent row as described above.

Author: Nikita Glukhov <n.gluhov@postgrespro.ru>
Author: Teodor Sigaev <teodor@sigaev.ru>
Author: Oleg Bartunov <obartunov@gmail.com>
Author: Alexander Korotkov <aekorotkov@gmail.com>
Author: Andrew Dunstan <andrew@dunslane.net>
Author: Amit Langote <amitlangote09@gmail.com>
Author: Jian He <jian.universality@gmail.com>

Reviewers have included (in no particular order):

Andres Freund, Alexander Korotkov, Pavel Stehule, Andrew Alsup,
Erik Rijkers, Zihong Yu, Himanshu Upadhyaya, Daniel Gustafsson,
Justin Pryzby, Álvaro Herrera, Jian He

Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru
Discussion: https://postgr.es/m/20220616233130.rparivafipt6doj3@alap3.anarazel.de
Discussion: https://postgr.es/m/abd9b83b-aa66-f230-3d6d-734817f0995d%40postgresql.org
Discussion: https://postgr.es/m/CA+HiwqE4XTdfb1nW=Ojoy_tQSRhYt-q_kb6i5d4xcKyrLC1Nbg@mail.gmail.com
This commit is contained in:
Amit Langote
2024-04-08 15:58:58 +09:00
parent f6a2529920
commit bb766cde63
17 changed files with 1209 additions and 33 deletions
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2
src/backend/catalog/sql_features.txt
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@@ -553,7 +553,7 @@ T823 SQL/JSON: PASSING clause YES
T824 JSON_TABLE: specific PLAN clause NO
T825 SQL/JSON: ON EMPTY and ON ERROR clauses YES
T826 General value expression in ON ERROR or ON EMPTY clauses YES
T827 JSON_TABLE: sibling NESTED COLUMNS clauses NO
T827 JSON_TABLE: sibling NESTED COLUMNS clauses YES
T828 JSON_QUERY YES
T829 JSON_QUERY: array wrapper options YES
T830 Enforcing unique keys in SQL/JSON constructor functions YES