[ESQL] Minor refactor for DataType

[ioanatia]

Minor refactor:

• Removes 2 unused methods from DataType
• Noticed that DataType and EsqlDataTypes had some duplicate methods so I removed the ones from EsqlDataTypes:

elasticsearch/x-pack/plugin/esql-core/src/main/java/org/elasticsearch/xpack/esql/core/type/DataType.java

Lines 216 to 218 in 6191fe3

	public static boolean isString(DataType t) {
	return t == KEYWORD || t == TEXT;
	}

elasticsearch/x-pack/plugin/esql-core/src/main/java/org/elasticsearch/xpack/esql/core/type/DataType.java

Lines 165 to 167 in 6191fe3

	public static DataType fromTypeName(String name) {
	return NAME_TO_TYPE.get(name.toLowerCase(Locale.ROOT));
	}

elasticsearch/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/type/EsqlDataTypes.java

Lines 34 to 40 in 6191fe3

	public static DataType fromTypeName(String name) {
	return DataType.fromTypeName(name.toLowerCase(Locale.ROOT));
	}
	public static boolean isString(DataType t) {
	return t == KEYWORD || t == TEXT;
	}

[ioanatia]

@elasticmachine test this please

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)

[not-napoleon]

LGTM. Thanks for cleaning this up!

[bpintea]

I think we'll want to keep this method here and remove the equivalent from EsqlDataTypes.java, which might be at some point removed entirely (similar to how isString() is kept here and has been removed from there). But this can be done at some subsequent refactor.
LGTM otherwise.

[ioanatia]

The implementation of the two is slightly different:

elasticsearch/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/type/EsqlDataTypes.java

Lines 85 to 93 in 39aa832

	public static boolean areCompatible(DataType left, DataType right) {
	if (left == right) {
	return true;
	} else {
	return (left == NULL || right == NULL)
	|| (DataType.isString(left) && DataType.isString(right))
	|| (left.isNumeric() && right.isNumeric());
	}
	}

I did not know what are the consequences of having the extra || (isDateTime(left) && isDateTime(right)); condition.

[bpintea]

I did not know what are the consequences of having the extra || (isDateTime(left) && isDateTime(right)); condition.

Right now, none. Since ESQL (unlike SQL, where that check was likely added) only has one datetime type (DATETIME), the check would be mostly superfluous, since for it to match, both types would have to be the same, so caught by the first equality check.

But once we'll have more than one type (like the upcoming nanos support, we'll likely need to add this check back. CC: @not-napoleon.