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Remove "invalid concatenation of jsonb objects" error case.

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The jsonb || jsonb operator arbitrarily rejected certain combinations
of scalar and non-scalar inputs, while being willing to concatenate
other combinations.  This was of course quite undocumented.  Rather
than trying to document it, let's just remove the restriction,
creating a uniform rule that unless we are handling an object-to-object
concatenation, non-array inputs are converted to one-element arrays,
resulting in an array-to-array concatenation.  (This does not change
the behavior for any case that didn't throw an error before.)

Per complaint from Joel Jacobson.  Back-patch to all supported branches.

Discussion: https://postgr.es/m/163099.1608312033@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2020-12-21 13:11:29 -05:00
parent be9c3cd186
commit 38d30a14b0
4 changed files with 99 additions and 47 deletions
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22
doc/src/sgml/func.sgml
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@ -14736,8 +14736,12 @@ table2-mapping
</para>
<para>
Concatenates two <type>jsonb</type> values.
Concatenating two objects generates an object with the union of their
Concatenating two arrays generates an array containing all the
elements of each input. Concatenating two objects generates an
object containing the union of their
keys, taking the second object's value when there are duplicate keys.
All other cases are treated by converting a non-array input into a
single-element array, and then proceeding as for two arrays.
Does not operate recursively: only the top-level array or object
structure is merged.
</para>
@ -14748,6 +14752,22 @@ table2-mapping
<para>
<literal>'{"a": "b"}'::jsonb || '{"c": "d"}'::jsonb</literal>
<returnvalue>{"a": "b", "c": "d"}</returnvalue>
</para>
<para>
<literal>'[1, 2]'::jsonb || '3'::jsonb</literal>
<returnvalue>[1, 2, 3]</returnvalue>
</para>
<para>
<literal>'{"a": "b"}'::jsonb || '42'::jsonb</literal>
<returnvalue>[{"a": "b"}, 42]</returnvalue>
</para>
<para>
To append an array to another array as a single entry, wrap it
in an additional layer of array, for example:
</para>
<para>
<literal>'[1, 2]'::jsonb || jsonb_build_array('[3, 4]'::jsonb)</literal>
<returnvalue>[1, 2, [3, 4]]</returnvalue>
</para></entry>
</row>