Stamatis Zampetakis created CALCITE-6832:
--------------------------------------------
Summary: Redundant fields/nullable entries in STRUCT serialization
to JSON
Key: CALCITE-6832
URL: https://issues.apache.org/jira/browse/CALCITE-6832
Project: Calcite
Issue Type: Bug
Affects Versions: 1.38.0
Reporter: Stamatis Zampetakis
Assignee: Stamatis Zampetakis
Fix For: 1.39.0
The JSON serialization of a {{RelDatatypeField}} of type STRUCT contains
redundant fields and nullable entries along with unnecessary nesting.
Consider for example, a field "address" of type STRUCT composed from the
following fields.
{code:java}
RelDataType type = typeFactory.builder()
.add("street", SqlTypeName.VARCHAR, 50)
.add("number", SqlTypeName.INTEGER)
.add("building", SqlTypeName.VARCHAR, 20).nullable(true)
.build();
RelDataTypeField address =
new RelDataTypeFieldImpl("address", 0, type);
{code}
At the moment, the JSON serialization for the field "address" is shown below.
{code:json}
{
"fields": {
"fields": [
{
"type": "VARCHAR",
"nullable": false,
"precision": 50,
"name": "street"
},
{
"type": "INTEGER",
"nullable": false,
"name": "number"
},
{
"type": "VARCHAR",
"nullable": true,
"precision": 20,
"name": "building"
}
],
"nullable": false
},
"nullable": false,
"name": "address"
}
{code}
Note that the "fields" key appears twice and there is an unnecessary wrapping
of a JSON array (inner "fields") inside a JSON object (outer "fields"). The
outer "fields" object cannot have more entries so it doesn't offer anything.
Moreover, observe that there are two {{"nullable":false}} entries and both
reflect the nullability of the "address" field.
The redundancy leads to wasted space and more convoluted representation that is
hard to follow especially when there are nested STRUCTS.
The same information could be represented using the following JSON
serialization:
{code:json}
{
"fields": [
{
"type": "VARCHAR",
"nullable": false,
"precision": 50,
"name": "street"
},
{
"type": "INTEGER",
"nullable": false,
"name": "number"
},
{
"type": "VARCHAR",
"nullable": true,
"precision": 20,
"name": "building"
}
],
"nullable": false,
"name": "address"
}
{code}
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