Add an option to @Field annotation to control property write rules [DATAMONGO-2551]

[spring-projects-issues]

isopov opened DATAMONGO-2551 and commented

In mongo it is possible to completely omit writing a field in collection if it is not needed in this document. This has a benefit of using sparse indexes on such field (or their modern replacement indexes with partial filters on exists=false). Also it reduces storage size. It seems that it would be beneficial to have an boolean option for Field annotation named omitNull (or any other name) that will allow to skip writing this field if it has null value

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No further details from DATAMONGO-2551

[christophstrobl]

The mapping layer by default does not write null values to the resulting org.bson.Document (see: MappingMongoConverter.java#L615).
In some scenarios is might make sense to allow persist null values, so that an $exits operator would still match, though the actual value is null.

On field level something like the following might make sense.

public @interface Field {

	// ...

	/**
	 * If set to {@literal true} {@literal null} values will be omitted.
	 * Setting the value to {@literal false} explicitly adds an entry for the given field
	 * holding {@literal null} as a value {@code 'fieldName' : null }.
	 * <p />
	 * <strong>NOTE</strong> Setting the value to {@literal false} may lead to increased document size.
	 * @return {@literal true} by default.
	 */
	boolean omitNull() default true;
}

Same could be applied to the @Document annotation or set via the Conversions API.

Happy to gather/discuss requirements & thoughts here to get a clear picture of the enhancement.