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Commit1c90345

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Fix conversion of JSON strings to JSON output columns in json_to_record().
json_to_record(), when an output column is declared as type json or jsonb,should emit the corresponding field of the input JSON object. But it gotthis slightly wrong when the field is just a string literal: it failed toescape the contents of the string. That typically resulted in syntaxerrors if the string contained any double quotes or backslashes.jsonb_to_record() handles such cases correctly, but I added correspondingtest cases for it too, to prevent future backsliding.Improve the documentation, as it provided only a very hand-wavydescription of the conversion rules used by these functions.Per bug report from Robert Vollmert. Back-patch to v10 where theerror was introduced (by commitcf35346).Note that PG 9.4 - 9.6 also get this case wrong, but differently so:they feed the de-escaped contents of the string literal to json[b]_in.That behavior is less obviously wrong, so possibly it's being depended onin the field, so I won't risk trying to make the older branches behavelike the newer ones.Discussion:https://postgr.es/m/D6921B37-BD8E-4664-8D5F-DB3525765DCD@vllmrt.net
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6 files changed

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6 files changed

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‎doc/src/sgml/func.sgml‎

Lines changed: 65 additions & 22 deletions
Original file line numberDiff line numberDiff line change
@@ -12006,29 +12006,72 @@ table2-mapping
1200612006
</note>
1200712007

1200812008
<note>
12009-
<para>
12010-
While the examples for the functions
12011-
<function>json_populate_record</function>,
12012-
<function>json_populate_recordset</function>,
12013-
<function>json_to_record</function> and
12014-
<function>json_to_recordset</function> use constants, the typical use
12015-
would be to reference a table in the <literal>FROM</literal> clause
12016-
and use one of its <type>json</type> or <type>jsonb</type> columns
12017-
as an argument to the function. Extracted key values can then be
12018-
referenced in other parts of the query, like <literal>WHERE</literal>
12019-
clauses and target lists. Extracting multiple values in this
12020-
way can improve performance over extracting them separately with
12021-
per-key operators.
12022-
</para>
12009+
<para>
12010+
The functions
12011+
<function>json[b]_populate_record</function>,
12012+
<function>json[b]_populate_recordset</function>,
12013+
<function>json[b]_to_record</function> and
12014+
<function>json[b]_to_recordset</function>
12015+
operate on a JSON object, or array of objects, and extract the values
12016+
associated with keys whose names match column names of the output row
12017+
type.
12018+
Object fields that do not correspond to any output column name are
12019+
ignored, and output columns that do not match any object field will be
12020+
filled with nulls.
12021+
To convert a JSON value to the SQL type of an output column, the
12022+
following rules are applied in sequence:
12023+
<itemizedlist spacing="compact">
12024+
<listitem>
12025+
<para>
12026+
A JSON null value is converted to a SQL null in all cases.
12027+
</para>
12028+
</listitem>
12029+
<listitem>
12030+
<para>
12031+
If the output column is of type <type>json</type>
12032+
or <type>jsonb</type>, the JSON value is just reproduced exactly.
12033+
</para>
12034+
</listitem>
12035+
<listitem>
12036+
<para>
12037+
If the output column is a composite (row) type, and the JSON value is
12038+
a JSON object, the fields of the object are converted to columns of
12039+
the output row type by recursive application of these rules.
12040+
</para>
12041+
</listitem>
12042+
<listitem>
12043+
<para>
12044+
Likewise, if the output column is an array type and the JSON value is
12045+
a JSON array, the elements of the JSON array are converted to elements
12046+
of the output array by recursive application of these rules.
12047+
</para>
12048+
</listitem>
12049+
<listitem>
12050+
<para>
12051+
Otherwise, if the JSON value is a string literal, the contents of the
12052+
string are fed to the input conversion function for the column's data
12053+
type.
12054+
</para>
12055+
</listitem>
12056+
<listitem>
12057+
<para>
12058+
Otherwise, the ordinary text representation of the JSON value is fed
12059+
to the input conversion function for the column's data type.
12060+
</para>
12061+
</listitem>
12062+
</itemizedlist>
12063+
</para>
1202312064

12024-
<para>
12025-
JSON keys are matched to identical column names in the target
12026-
row type. JSON type coercion for these functions is <quote>best
12027-
effort</quote> and may not result in desired values for some types.
12028-
JSON fields that do not appear in the target row type will be
12029-
omitted from the output, and target columns that do not match any
12030-
JSON field will simply be NULL.
12031-
</para>
12065+
<para>
12066+
While the examples for these functions use constants, the typical use
12067+
would be to reference a table in the <literal>FROM</literal> clause
12068+
and use one of its <type>json</type> or <type>jsonb</type> columns
12069+
as an argument to the function. Extracted key values can then be
12070+
referenced in other parts of the query, like <literal>WHERE</literal>
12071+
clauses and target lists. Extracting multiple values in this
12072+
way can improve performance over extracting them separately with
12073+
per-key operators.
12074+
</para>
1203212075
</note>
1203312076

1203412077
<note>

‎src/backend/utils/adt/jsonfuncs.c‎

Lines changed: 16 additions & 21 deletions
Original file line numberDiff line numberDiff line change
@@ -2803,34 +2803,29 @@ populate_scalar(ScalarIOData *io, Oid typid, int32 typmod, JsValue *jsv)
28032803

28042804
json=jsv->val.json.str;
28052805
Assert(json);
2806-
2807-
/* already done the hard work in the json case */
2808-
if ((typid==JSONOID||typid==JSONBOID)&&
2809-
jsv->val.json.type==JSON_TOKEN_STRING)
2810-
{
2811-
/*
2812-
* Add quotes around string value (should be already escaped) if
2813-
* converting to json/jsonb.
2814-
*/
2815-
2816-
if (len<0)
2817-
len=strlen(json);
2818-
2819-
str=palloc(len+sizeof(char)*3);
2820-
str[0]='"';
2821-
memcpy(&str[1],json,len);
2822-
str[len+1]='"';
2823-
str[len+2]='\0';
2824-
}
2825-
elseif (len >=0)
2806+
if (len >=0)
28262807
{
28272808
/* Need to copy non-null-terminated string */
28282809
str=palloc(len+1*sizeof(char));
28292810
memcpy(str,json,len);
28302811
str[len]='\0';
28312812
}
28322813
else
2833-
str=json;/* null-terminated string */
2814+
str=json;/* string is already null-terminated */
2815+
2816+
/* If converting to json/jsonb, make string into valid JSON literal */
2817+
if ((typid==JSONOID||typid==JSONBOID)&&
2818+
jsv->val.json.type==JSON_TOKEN_STRING)
2819+
{
2820+
StringInfoDatabuf;
2821+
2822+
initStringInfo(&buf);
2823+
escape_json(&buf,str);
2824+
/* free temporary buffer */
2825+
if (str!=json)
2826+
pfree(str);
2827+
str=buf.data;
2828+
}
28342829
}
28352830
else
28362831
{

‎src/test/regress/expected/json.out‎

Lines changed: 36 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2276,6 +2276,42 @@ select * from json_to_record('{"ia2": [[[1], [2], [3]]]}') as x(ia2 int4[][]);
22762276
{{{1},{2},{3}}}
22772277
(1 row)
22782278

2279+
select * from json_to_record('{"out": {"key": 1}}') as x(out json);
2280+
out
2281+
------------
2282+
{"key": 1}
2283+
(1 row)
2284+
2285+
select * from json_to_record('{"out": [{"key": 1}]}') as x(out json);
2286+
out
2287+
--------------
2288+
[{"key": 1}]
2289+
(1 row)
2290+
2291+
select * from json_to_record('{"out": "{\"key\": 1}"}') as x(out json);
2292+
out
2293+
----------------
2294+
"{\"key\": 1}"
2295+
(1 row)
2296+
2297+
select * from json_to_record('{"out": {"key": 1}}') as x(out jsonb);
2298+
out
2299+
------------
2300+
{"key": 1}
2301+
(1 row)
2302+
2303+
select * from json_to_record('{"out": [{"key": 1}]}') as x(out jsonb);
2304+
out
2305+
--------------
2306+
[{"key": 1}]
2307+
(1 row)
2308+
2309+
select * from json_to_record('{"out": "{\"key\": 1}"}') as x(out jsonb);
2310+
out
2311+
----------------
2312+
"{\"key\": 1}"
2313+
(1 row)
2314+
22792315
-- json_strip_nulls
22802316
select json_strip_nulls(null);
22812317
json_strip_nulls

‎src/test/regress/expected/jsonb.out‎

Lines changed: 36 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2652,6 +2652,42 @@ select * from jsonb_to_record('{"ia2": [[[1], [2], [3]]]}') as x(ia2 int4[][]);
26522652
{{{1},{2},{3}}}
26532653
(1 row)
26542654

2655+
select * from jsonb_to_record('{"out": {"key": 1}}') as x(out json);
2656+
out
2657+
------------
2658+
{"key": 1}
2659+
(1 row)
2660+
2661+
select * from jsonb_to_record('{"out": [{"key": 1}]}') as x(out json);
2662+
out
2663+
--------------
2664+
[{"key": 1}]
2665+
(1 row)
2666+
2667+
select * from jsonb_to_record('{"out": "{\"key\": 1}"}') as x(out json);
2668+
out
2669+
----------------
2670+
"{\"key\": 1}"
2671+
(1 row)
2672+
2673+
select * from jsonb_to_record('{"out": {"key": 1}}') as x(out jsonb);
2674+
out
2675+
------------
2676+
{"key": 1}
2677+
(1 row)
2678+
2679+
select * from jsonb_to_record('{"out": [{"key": 1}]}') as x(out jsonb);
2680+
out
2681+
--------------
2682+
[{"key": 1}]
2683+
(1 row)
2684+
2685+
select * from jsonb_to_record('{"out": "{\"key\": 1}"}') as x(out jsonb);
2686+
out
2687+
----------------
2688+
"{\"key\": 1}"
2689+
(1 row)
2690+
26552691
-- test type info caching in jsonb_populate_record()
26562692
CREATE TEMP TABLE jsbpoptest (js jsonb);
26572693
INSERT INTO jsbpoptest

‎src/test/regress/sql/json.sql‎

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -742,6 +742,13 @@ select * from json_to_record('{"ia2": [1, 2, 3]}') as x(ia2 int[][]);
742742
select*from json_to_record('{"ia2": [[1, 2], [3, 4]]}')as x(ia2 int4[][]);
743743
select*from json_to_record('{"ia2": [[[1], [2], [3]]]}')as x(ia2 int4[][]);
744744

745+
select*from json_to_record('{"out": {"key": 1}}')as x(out json);
746+
select*from json_to_record('{"out": [{"key": 1}]}')as x(out json);
747+
select*from json_to_record('{"out": "{\"key\": 1}"}')as x(out json);
748+
select*from json_to_record('{"out": {"key": 1}}')as x(out jsonb);
749+
select*from json_to_record('{"out": [{"key": 1}]}')as x(out jsonb);
750+
select*from json_to_record('{"out": "{\"key\": 1}"}')as x(out jsonb);
751+
745752
-- json_strip_nulls
746753

747754
select json_strip_nulls(null);

‎src/test/regress/sql/jsonb.sql‎

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -709,6 +709,13 @@ select * from jsonb_to_record('{"ia2": [1, 2, 3]}') as x(ia2 int[][]);
709709
select*from jsonb_to_record('{"ia2": [[1, 2], [3, 4]]}')as x(ia2 int4[][]);
710710
select*from jsonb_to_record('{"ia2": [[[1], [2], [3]]]}')as x(ia2 int4[][]);
711711

712+
select*from jsonb_to_record('{"out": {"key": 1}}')as x(out json);
713+
select*from jsonb_to_record('{"out": [{"key": 1}]}')as x(out json);
714+
select*from jsonb_to_record('{"out": "{\"key\": 1}"}')as x(out json);
715+
select*from jsonb_to_record('{"out": {"key": 1}}')as x(out jsonb);
716+
select*from jsonb_to_record('{"out": [{"key": 1}]}')as x(out jsonb);
717+
select*from jsonb_to_record('{"out": "{\"key\": 1}"}')as x(out jsonb);
718+
712719
-- test type info caching in jsonb_populate_record()
713720
CREATE TEMP TABLE jsbpoptest (js jsonb);
714721

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