.Net: [MEVD] Create indexes on data properties when IsFilterable is true

[roji]

[adamsitnik]

I took a brief look at the issue and it seems that other connectors also don't create dedicated indexes in such cases.

Example: PostgreSQL creates indexes only for the vector properties:

semantic-kernel/dotnet/src/Connectors/Connectors.Memory.Postgres/PostgresVectorStoreDbClient.cs

Lines 74 to 78 in d35d0c9

	var createIndexCommands =
	PostgresVectorStoreRecordPropertyMapping.GetVectorIndexInfo(properties)
	.Select(index =>
	this._sqlBuilder.BuildCreateVectorIndexCommand(this._schema, tableName, index.column, index.kind, index.function, ifNotExists)
	);

semantic-kernel/dotnet/src/Connectors/Connectors.Memory.Postgres/PostgresVectorStoreRecordPropertyMapping.cs

Lines 209 to 214 in d35d0c9

	public static List<(string column, string kind, string function)> GetVectorIndexInfo(IReadOnlyList<VectorStoreRecordProperty> properties)
	{
	var vectorIndexesToCreate = new List<(string column, string kind, string function)>();
	foreach (var property in properties)
	{
	if (property is VectorStoreRecordVectorProperty vectorProperty)

[roji]

Good catch, thanks for looking at the other connectors (is it true only for the other relational ones, or also for the other non-relational ones? If so, that would mean that IsFilterable is effectively being ignored...

I've modified the title of the issue, for it to track index creation in general. That's of course more work... /cc @westey-m @dmytrostruk