Currently the way some actions work, we receive an error during analysis
phase. For example, doing a "SELECT * FROM non_existent_table" will return
an analysis exception as the NoSuchTableException is captured and replaced.
Other actions like the "ShowNamespaceExec" call catalog methods directly
and directly throw a NoSuchNamsSpaceException
While I don't think the difference here is a big deal, It would be nice if
we could have just one set of behaviors. My interest here was being able to
throw custom NoSuchTable and NoSuchNameSpace exceptions
which contained naming suggestions.
For example
*SELECT * from catalog.keyspace.tuble*
Could optionally return an analysis exception which suggested other names
of tables (or keyspaces) which contained like
"Could not find keyspace.tuble, found a near hit: keyspace.table"
While I have the code to do this internally within my own catalog because
of previous functionality,
I cannot surface this information to the user anymore in DSV2 because of
the way the exceptions are handled.
Given this, I'm wondering if we could wrap and rethrow the NoSuchExceptions
or would it be better for catalogs to support an interfaces like
trait SupportsTableNamingSuggestions extends TableCatalog {
val matchThreshold = 0.7
val matcher: (String, String) => Double = JaroWinkler // Or some other
string comparison algorithm
/** Given an identifier, return a list of identifiers that it may have
been mistaken for"
default def tableSuggestions(missingIdent: Identifier): Seq[Ident] {
for (table <- getTables(ident.namespace) if matcher(missingIdent.table,
ident.table) > matchThreshold) yield {
table
}
}
}
// And another for namespaces
Then on analysis failures, if the catalog supports this trait we could
supplement the analysis failure with some helpful info. We could leave this
as a trait for
those implementations whose listing of tables or namespaces is costly.
Thanks for your consideration, this is the kind of feature that I think is
very useful to end users and we can add with pretty limited cost,
Russ
