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

2 files changed, 216 insertions, 0 deletions

diff --git a/src/test/regress/expected/jsonb.out b/src/test/regress/expected/jsonb.out
index 46bf2e23530..5b5510c4fdc 100644
--- a/src/test/regress/expected/jsonb.out
+++ b/src/test/regress/expected/jsonb.out
@@ -4999,6 +4999,141 @@ select * from test_jsonb_subscript;
   3 | [1]
 (3 rows)
 
+-- Fill the gaps logic
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '[0]');
+update test_jsonb_subscript set test_json[5] = '1';
+select * from test_jsonb_subscript;
+ id |           test_json            
+----+--------------------------------
+  1 | [0, null, null, null, null, 1]
+(1 row)
+
+update test_jsonb_subscript set test_json[-4] = '1';
+select * from test_jsonb_subscript;
+ id |          test_json          
+----+-----------------------------
+  1 | [0, null, 1, null, null, 1]
+(1 row)
+
+update test_jsonb_subscript set test_json[-8] = '1';
+ERROR:  path element at position 1 is out of range: -8
+select * from test_jsonb_subscript;
+ id |          test_json          
+----+-----------------------------
+  1 | [0, null, 1, null, null, 1]
+(1 row)
+
+-- keep consistent values position
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '[]');
+update test_jsonb_subscript set test_json[5] = '1';
+select * from test_jsonb_subscript;
+ id |             test_json             
+----+-----------------------------------
+  1 | [null, null, null, null, null, 1]
+(1 row)
+
+-- create the whole path
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '{}');
+update test_jsonb_subscript set test_json['a'][0]['b'][0]['c'] = '1';
+select * from test_jsonb_subscript;
+ id |         test_json          
+----+----------------------------
+  1 | {"a": [{"b": [{"c": 1}]}]}
+(1 row)
+
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '{}');
+update test_jsonb_subscript set test_json['a'][2]['b'][2]['c'][2] = '1';
+select * from test_jsonb_subscript;
+ id |                            test_json                             
+----+------------------------------------------------------------------
+  1 | {"a": [null, null, {"b": [null, null, {"c": [null, null, 1]}]}]}
+(1 row)
+
+-- create the whole path with already existing keys
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '{"b": 1}');
+update test_jsonb_subscript set test_json['a'][0] = '2';
+select * from test_jsonb_subscript;
+ id |     test_json      
+----+--------------------
+  1 | {"a": [2], "b": 1}
+(1 row)
+
+-- the start jsonb is an object, first subscript is treated as a key
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '{}');
+update test_jsonb_subscript set test_json[0]['a'] = '1';
+select * from test_jsonb_subscript;
+ id |    test_json    
+----+-----------------
+  1 | {"0": {"a": 1}}
+(1 row)
+
+-- the start jsonb is an array
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '[]');
+update test_jsonb_subscript set test_json[0]['a'] = '1';
+update test_jsonb_subscript set test_json[2]['b'] = '2';
+select * from test_jsonb_subscript;
+ id |         test_json          
+----+----------------------------
+  1 | [{"a": 1}, null, {"b": 2}]
+(1 row)
+
+-- overwriting an existing path
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '{}');
+update test_jsonb_subscript set test_json['a']['b'][1] = '1';
+update test_jsonb_subscript set test_json['a']['b'][10] = '1';
+select * from test_jsonb_subscript;
+ id |                                 test_json                                  
+----+----------------------------------------------------------------------------
+  1 | {"a": {"b": [null, 1, null, null, null, null, null, null, null, null, 1]}}
+(1 row)
+
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '[]');
+update test_jsonb_subscript set test_json[0][0][0] = '1';
+update test_jsonb_subscript set test_json[0][0][1] = '1';
+select * from test_jsonb_subscript;
+ id | test_json  
+----+------------
+  1 | [[[1, 1]]]
+(1 row)
+
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '{}');
+update test_jsonb_subscript set test_json['a']['b'][10] = '1';
+update test_jsonb_subscript set test_json['a'][10][10] = '1';
+select * from test_jsonb_subscript;
+ id |                                                                      test_json                                                                       
+----+------------------------------------------------------------------------------------------------------------------------------------------------------
+  1 | {"a": {"b": [null, null, null, null, null, null, null, null, null, null, 1], "10": [null, null, null, null, null, null, null, null, null, null, 1]}}
+(1 row)
+
+-- an empty sub element
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '{"a": {}}');
+update test_jsonb_subscript set test_json['a']['b']['c'][2] = '1';
+select * from test_jsonb_subscript;
+ id |              test_json               
+----+--------------------------------------
+  1 | {"a": {"b": {"c": [null, null, 1]}}}
+(1 row)
+
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '{"a": []}');
+update test_jsonb_subscript set test_json['a'][1]['c'][2] = '1';
+select * from test_jsonb_subscript;
+ id |               test_json               
+----+---------------------------------------
+  1 | {"a": [null, {"c": [null, null, 1]}]}
+(1 row)
+
 -- jsonb to tsvector
 select to_tsvector('{"a": "aaa bbb ddd ccc", "b": ["eee fff ggg"], "c": {"d": "hhh iii"}}'::jsonb);
                                 to_tsvector                                
diff --git a/src/test/regress/sql/jsonb.sql b/src/test/regress/sql/jsonb.sql
index 20aa8fe0e24..0320db0ea46 100644
--- a/src/test/regress/sql/jsonb.sql
+++ b/src/test/regress/sql/jsonb.sql
@@ -1290,6 +1290,87 @@ update test_jsonb_subscript set test_json = NULL where id = 3;
 update test_jsonb_subscript set test_json[0] = '1';
 select * from test_jsonb_subscript;
 
+-- Fill the gaps logic
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '[0]');
+
+update test_jsonb_subscript set test_json[5] = '1';
+select * from test_jsonb_subscript;
+
+update test_jsonb_subscript set test_json[-4] = '1';
+select * from test_jsonb_subscript;
+
+update test_jsonb_subscript set test_json[-8] = '1';
+select * from test_jsonb_subscript;
+
+-- keep consistent values position
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '[]');
+
+update test_jsonb_subscript set test_json[5] = '1';
+select * from test_jsonb_subscript;
+
+-- create the whole path
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '{}');
+update test_jsonb_subscript set test_json['a'][0]['b'][0]['c'] = '1';
+select * from test_jsonb_subscript;
+
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '{}');
+update test_jsonb_subscript set test_json['a'][2]['b'][2]['c'][2] = '1';
+select * from test_jsonb_subscript;
+
+-- create the whole path with already existing keys
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '{"b": 1}');
+update test_jsonb_subscript set test_json['a'][0] = '2';
+select * from test_jsonb_subscript;
+
+-- the start jsonb is an object, first subscript is treated as a key
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '{}');
+update test_jsonb_subscript set test_json[0]['a'] = '1';
+select * from test_jsonb_subscript;
+
+-- the start jsonb is an array
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '[]');
+update test_jsonb_subscript set test_json[0]['a'] = '1';
+update test_jsonb_subscript set test_json[2]['b'] = '2';
+select * from test_jsonb_subscript;
+
+-- overwriting an existing path
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '{}');
+update test_jsonb_subscript set test_json['a']['b'][1] = '1';
+update test_jsonb_subscript set test_json['a']['b'][10] = '1';
+select * from test_jsonb_subscript;
+
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '[]');
+update test_jsonb_subscript set test_json[0][0][0] = '1';
+update test_jsonb_subscript set test_json[0][0][1] = '1';
+select * from test_jsonb_subscript;
+
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '{}');
+update test_jsonb_subscript set test_json['a']['b'][10] = '1';
+update test_jsonb_subscript set test_json['a'][10][10] = '1';
+select * from test_jsonb_subscript;
+
+-- an empty sub element
+
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '{"a": {}}');
+update test_jsonb_subscript set test_json['a']['b']['c'][2] = '1';
+select * from test_jsonb_subscript;
+
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '{"a": []}');
+update test_jsonb_subscript set test_json['a'][1]['c'][2] = '1';
+select * from test_jsonb_subscript;
+
 -- jsonb to tsvector
 select to_tsvector('{"a": "aaa bbb ddd ccc", "b": ["eee fff ggg"], "c": {"d": "hhh iii"}}'::jsonb);