<note>

<para>

In <function>json_populate_record</function>, <function>json_populate_recordset</function>,

<function>json_to_record</function> and <function>json_to_recordset</function>,

type coercion from the JSON is <quote>best effort</quote> and may not result

in desired values for some types. JSON keys are matched to

identical column names in the target row type. JSON fields that do not

appear in the target row type will be omitted from the output, and

target columns that do not match any JSON field will simply be NULL.

While the examples for the functions

<function>json_populate_record</function>,

<function>json_populate_recordset</function>,

<function>json_to_record</function> and

<function>json_to_recordset</function> use constants, the typical use

would be to reference a table in the <literal>FROM</literal> clause

and use one of its <type>json</type> or <type>jsonb</type> columns

as an argument to the function. Extracted key values can then be

referenced in other parts of the query, like <literal>WHERE</literal>

clauses and target lists. Extracting multiple values in this

way can improve performance over extracting them separately with

per-key operators.

</para>

<para>

JSON keys are matched to identical column names in the target

row type. JSON type coercion for these functions is <quote>best

effort</quote> and may not result in desired values for some types.

JSON fields that do not appear in the target row type will be

omitted from the output, and target columns that do not match any

JSON field will simply be NULL.

</para>

</note>