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Commitb6f5689

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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
1 parent52ad5fc commitb6f5689

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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
@@ -11864,29 +11864,72 @@ table2-mapping
1186411864
</note>
1186511865

1186611866
<note>
11867-
<para>
11868-
While the examples for the functions
11869-
<function>json_populate_record</function>,
11870-
<function>json_populate_recordset</function>,
11871-
<function>json_to_record</function> and
11872-
<function>json_to_recordset</function> use constants, the typical use
11873-
would be to reference a table in the <literal>FROM</literal> clause
11874-
and use one of its <type>json</type> or <type>jsonb</type> columns
11875-
as an argument to the function. Extracted key values can then be
11876-
referenced in other parts of the query, like <literal>WHERE</literal>
11877-
clauses and target lists. Extracting multiple values in this
11878-
way can improve performance over extracting them separately with
11879-
per-key operators.
11880-
</para>
11867+
<para>
11868+
The functions
11869+
<function>json[b]_populate_record</function>,
11870+
<function>json[b]_populate_recordset</function>,
11871+
<function>json[b]_to_record</function> and
11872+
<function>json[b]_to_recordset</function>
11873+
operate on a JSON object, or array of objects, and extract the values
11874+
associated with keys whose names match column names of the output row
11875+
type.
11876+
Object fields that do not correspond to any output column name are
11877+
ignored, and output columns that do not match any object field will be
11878+
filled with nulls.
11879+
To convert a JSON value to the SQL type of an output column, the
11880+
following rules are applied in sequence:
11881+
<itemizedlist spacing="compact">
11882+
<listitem>
11883+
<para>
11884+
A JSON null value is converted to a SQL null in all cases.
11885+
</para>
11886+
</listitem>
11887+
<listitem>
11888+
<para>
11889+
If the output column is of type <type>json</type>
11890+
or <type>jsonb</type>, the JSON value is just reproduced exactly.
11891+
</para>
11892+
</listitem>
11893+
<listitem>
11894+
<para>
11895+
If the output column is a composite (row) type, and the JSON value is
11896+
a JSON object, the fields of the object are converted to columns of
11897+
the output row type by recursive application of these rules.
11898+
</para>
11899+
</listitem>
11900+
<listitem>
11901+
<para>
11902+
Likewise, if the output column is an array type and the JSON value is
11903+
a JSON array, the elements of the JSON array are converted to elements
11904+
of the output array by recursive application of these rules.
11905+
</para>
11906+
</listitem>
11907+
<listitem>
11908+
<para>
11909+
Otherwise, if the JSON value is a string literal, the contents of the
11910+
string are fed to the input conversion function for the column's data
11911+
type.
11912+
</para>
11913+
</listitem>
11914+
<listitem>
11915+
<para>
11916+
Otherwise, the ordinary text representation of the JSON value is fed
11917+
to the input conversion function for the column's data type.
11918+
</para>
11919+
</listitem>
11920+
</itemizedlist>
11921+
</para>
1188111922

11882-
<para>
11883-
JSON keys are matched to identical column names in the target
11884-
row type. JSON type coercion for these functions is <quote>best
11885-
effort</quote> and may not result in desired values for some types.
11886-
JSON fields that do not appear in the target row type will be
11887-
omitted from the output, and target columns that do not match any
11888-
JSON field will simply be NULL.
11889-
</para>
11923+
<para>
11924+
While the examples for these functions use constants, the typical use
11925+
would be to reference a table in the <literal>FROM</literal> clause
11926+
and use one of its <type>json</type> or <type>jsonb</type> columns
11927+
as an argument to the function. Extracted key values can then be
11928+
referenced in other parts of the query, like <literal>WHERE</literal>
11929+
clauses and target lists. Extracting multiple values in this
11930+
way can improve performance over extracting them separately with
11931+
per-key operators.
11932+
</para>
1189011933
</note>
1189111934

1189211935
<note>

‎src/backend/utils/adt/jsonfuncs.c‎

Lines changed: 16 additions & 21 deletions
Original file line numberDiff line numberDiff line change
@@ -2762,34 +2762,29 @@ populate_scalar(ScalarIOData *io, Oid typid, int32 typmod, JsValue *jsv)
27622762

27632763
json=jsv->val.json.str;
27642764
Assert(json);
2765-
2766-
/* already done the hard work in the json case */
2767-
if ((typid==JSONOID||typid==JSONBOID)&&
2768-
jsv->val.json.type==JSON_TOKEN_STRING)
2769-
{
2770-
/*
2771-
* Add quotes around string value (should be already escaped) if
2772-
* converting to json/jsonb.
2773-
*/
2774-
2775-
if (len<0)
2776-
len=strlen(json);
2777-
2778-
str=palloc(len+sizeof(char)*3);
2779-
str[0]='"';
2780-
memcpy(&str[1],json,len);
2781-
str[len+1]='"';
2782-
str[len+2]='\0';
2783-
}
2784-
elseif (len >=0)
2765+
if (len >=0)
27852766
{
27862767
/* Need to copy non-null-terminated string */
27872768
str=palloc(len+1*sizeof(char));
27882769
memcpy(str,json,len);
27892770
str[len]='\0';
27902771
}
27912772
else
2792-
str=json;/* null-terminated string */
2773+
str=json;/* string is already null-terminated */
2774+
2775+
/* If converting to json/jsonb, make string into valid JSON literal */
2776+
if ((typid==JSONOID||typid==JSONBOID)&&
2777+
jsv->val.json.type==JSON_TOKEN_STRING)
2778+
{
2779+
StringInfoDatabuf;
2780+
2781+
initStringInfo(&buf);
2782+
escape_json(&buf,str);
2783+
/* free temporary buffer */
2784+
if (str!=json)
2785+
pfree(str);
2786+
str=buf.data;
2787+
}
27932788
}
27942789
else
27952790
{

‎src/test/regress/expected/json.out‎

Lines changed: 36 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2200,6 +2200,42 @@ select * from json_to_record('{"ia2": [[[1], [2], [3]]]}') as x(ia2 int4[][]);
22002200
{{{1},{2},{3}}}
22012201
(1 row)
22022202

2203+
select * from json_to_record('{"out": {"key": 1}}') as x(out json);
2204+
out
2205+
------------
2206+
{"key": 1}
2207+
(1 row)
2208+
2209+
select * from json_to_record('{"out": [{"key": 1}]}') as x(out json);
2210+
out
2211+
--------------
2212+
[{"key": 1}]
2213+
(1 row)
2214+
2215+
select * from json_to_record('{"out": "{\"key\": 1}"}') as x(out json);
2216+
out
2217+
----------------
2218+
"{\"key\": 1}"
2219+
(1 row)
2220+
2221+
select * from json_to_record('{"out": {"key": 1}}') as x(out jsonb);
2222+
out
2223+
------------
2224+
{"key": 1}
2225+
(1 row)
2226+
2227+
select * from json_to_record('{"out": [{"key": 1}]}') as x(out jsonb);
2228+
out
2229+
--------------
2230+
[{"key": 1}]
2231+
(1 row)
2232+
2233+
select * from json_to_record('{"out": "{\"key\": 1}"}') as x(out jsonb);
2234+
out
2235+
----------------
2236+
"{\"key\": 1}"
2237+
(1 row)
2238+
22032239
-- json_strip_nulls
22042240
select json_strip_nulls(null);
22052241
json_strip_nulls

‎src/test/regress/expected/jsonb.out‎

Lines changed: 36 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2578,6 +2578,42 @@ select * from jsonb_to_record('{"ia2": [[[1], [2], [3]]]}') as x(ia2 int4[][]);
25782578
{{{1},{2},{3}}}
25792579
(1 row)
25802580

2581+
select * from jsonb_to_record('{"out": {"key": 1}}') as x(out json);
2582+
out
2583+
------------
2584+
{"key": 1}
2585+
(1 row)
2586+
2587+
select * from jsonb_to_record('{"out": [{"key": 1}]}') as x(out json);
2588+
out
2589+
--------------
2590+
[{"key": 1}]
2591+
(1 row)
2592+
2593+
select * from jsonb_to_record('{"out": "{\"key\": 1}"}') as x(out json);
2594+
out
2595+
----------------
2596+
"{\"key\": 1}"
2597+
(1 row)
2598+
2599+
select * from jsonb_to_record('{"out": {"key": 1}}') as x(out jsonb);
2600+
out
2601+
------------
2602+
{"key": 1}
2603+
(1 row)
2604+
2605+
select * from jsonb_to_record('{"out": [{"key": 1}]}') as x(out jsonb);
2606+
out
2607+
--------------
2608+
[{"key": 1}]
2609+
(1 row)
2610+
2611+
select * from jsonb_to_record('{"out": "{\"key\": 1}"}') as x(out jsonb);
2612+
out
2613+
----------------
2614+
"{\"key\": 1}"
2615+
(1 row)
2616+
25812617
-- test type info caching in jsonb_populate_record()
25822618
CREATE TEMP TABLE jsbpoptest (js jsonb);
25832619
INSERT INTO jsbpoptest

‎src/test/regress/sql/json.sql‎

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -712,6 +712,13 @@ select * from json_to_record('{"ia2": [1, 2, 3]}') as x(ia2 int[][]);
712712
select*from json_to_record('{"ia2": [[1, 2], [3, 4]]}')as x(ia2 int4[][]);
713713
select*from json_to_record('{"ia2": [[[1], [2], [3]]]}')as x(ia2 int4[][]);
714714

715+
select*from json_to_record('{"out": {"key": 1}}')as x(out json);
716+
select*from json_to_record('{"out": [{"key": 1}]}')as x(out json);
717+
select*from json_to_record('{"out": "{\"key\": 1}"}')as x(out json);
718+
select*from json_to_record('{"out": {"key": 1}}')as x(out jsonb);
719+
select*from json_to_record('{"out": [{"key": 1}]}')as x(out jsonb);
720+
select*from json_to_record('{"out": "{\"key\": 1}"}')as x(out jsonb);
721+
715722
-- json_strip_nulls
716723

717724
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
@@ -681,6 +681,13 @@ select * from jsonb_to_record('{"ia2": [1, 2, 3]}') as x(ia2 int[][]);
681681
select*from jsonb_to_record('{"ia2": [[1, 2], [3, 4]]}')as x(ia2 int4[][]);
682682
select*from jsonb_to_record('{"ia2": [[[1], [2], [3]]]}')as x(ia2 int4[][]);
683683

684+
select*from jsonb_to_record('{"out": {"key": 1}}')as x(out json);
685+
select*from jsonb_to_record('{"out": [{"key": 1}]}')as x(out json);
686+
select*from jsonb_to_record('{"out": "{\"key\": 1}"}')as x(out json);
687+
select*from jsonb_to_record('{"out": {"key": 1}}')as x(out jsonb);
688+
select*from jsonb_to_record('{"out": [{"key": 1}]}')as x(out jsonb);
689+
select*from jsonb_to_record('{"out": "{\"key\": 1}"}')as x(out jsonb);
690+
684691
-- test type info caching in jsonb_populate_record()
685692
CREATE TEMP TABLE jsbpoptest (js jsonb);
686693

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