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| author | Alexander Korotkov <akorotkov@postgresql.org> | 2021-01-31 23:51:01 +0300 |
|---|---|---|
| committer | Alexander Korotkov <akorotkov@postgresql.org> | 2021-01-31 23:51:01 +0300 |
| commit | 81fcc72e66222357f9bccce3eeda62eb2cb29849 (patch) | |
| tree | e75d796379677c30799a25215ac64ee2fbf44710 /doc/src | |
| parent | 676887a3b0b8e3c0348ac3f82ab0d16e9a24bd43 (diff) | |
| download | postgresql-81fcc72e66222357f9bccce3eeda62eb2cb29849.tar.gz postgresql-81fcc72e66222357f9bccce3eeda62eb2cb29849.zip | |
Filling array gaps during jsonb subscripting
This commit introduces two new flags for jsonb assignment:
* JB_PATH_FILL_GAPS: Appending array elements on the specified position, gaps
are filled with nulls (similar to the JavaScript behavior). This mode also
instructs to create the whole path in a jsonb object if some part of the
path (more than just the last element) is not present.
* JB_PATH_CONSISTENT_POSITION: Assigning keeps array positions consistent by
preventing prepending of elements.
Both flags are used only in jsonb subscripting assignment.
Initially proposed by Nikita Glukhov based on polymorphic subscripting
patch, but transformed into an independent change.
Discussion: https://postgr.es/m/CA%2Bq6zcV8qvGcDXurwwgUbwACV86Th7G80pnubg42e-p9gsSf%3Dg%40mail.gmail.com
Discussion: https://postgr.es/m/CA%2Bq6zcX3mdxGCgdThzuySwH-ApyHHM-G4oB1R0fn0j2hZqqkLQ%40mail.gmail.com
Discussion: https://postgr.es/m/CA%2Bq6zcVDuGBv%3DM0FqBYX8DPebS3F_0KQ6OVFobGJPM507_SZ_w%40mail.gmail.com
Discussion: https://postgr.es/m/CA%2Bq6zcVovR%2BXY4mfk-7oNk-rF91gH0PebnNfuUjuuDsyHjOcVA%40mail.gmail.com
Author: Dmitry Dolgov
Reviewed-by: Tom Lane, Arthur Zakirov, Pavel Stehule, Dian M Fay
Reviewed-by: Andrew Dunstan, Chapman Flack, Merlin Moncure, Peter Geoghegan
Reviewed-by: Alvaro Herrera, Jim Nasby, Josh Berkus, Victor Wagner
Reviewed-by: Aleksander Alekseev, Robert Haas, Oleg Bartunov
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/json.sgml | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/doc/src/sgml/json.sgml b/doc/src/sgml/json.sgml index 3ace5e444b0..07bd19f9742 100644 --- a/doc/src/sgml/json.sgml +++ b/doc/src/sgml/json.sgml @@ -650,6 +650,30 @@ UPDATE table_name SET jsonb_field['a'] = '1'; UPDATE table_name SET jsonb_field[0] = '1'; </programlisting> + If an index is specified for an array containing too few elements, + <literal>NULL</literal> elements will be appended until the index is reachable + and the value can be set. + +<programlisting> +-- Where jsonb_field was [], it is now [null, null, 2]; +-- where jsonb_field was [0], it is now [0, null, 2] +UPDATE table_name SET jsonb_field[2] = '2'; +</programlisting> + + A <type>jsonb</type> value will accept assignments to nonexistent subscript + paths as long as the last existing path key is an object or an array. Since + the final subscript is not traversed, it may be an object key. Nested arrays + will be created and <literal>NULL</literal>-padded according to the path until + the value can be placed appropriately. + +<programlisting> +-- Where jsonb_field was {}, it is now {'a': [{'b': 1}]} +UPDATE table_name SET jsonb_field['a'][0]['b'] = '1'; + +-- Where jsonb_field was [], it is now [{'a': 1}] +UPDATE table_name SET jsonb_field[0]['a'] = '1'; +</programlisting> + </para> </sect2> |