The active config object within the current scope. See SQLConf.get for more information.

Completely overwrite the top scope state with operator output.

This method is called by the Resolver when we've calculated the output of an operator that is being resolved. The new output is calculated based on the outputs of operator's children.

Example for SubqueryAlias, here we rewrite the top NameScope's attributes to prepend subquery qualifier to their names:

val qualifier = sa.identifier.qualifier :+ sa.alias
scope.overwriteTop(scope.output.map(attribute => attribute.withQualifier(qualifier)))

Trivially, we would call this method for every operator in the query plan, however some operators just propagate the output of their children without any changes, so we can omit this call for them (e.g. Filter).

This method should be preferred over withNewScope.

Execute body in a context of a fresh scope.

This method is called by the Resolver before recursing into the operator's child resolution _only_ in cases where a fresh scope is required.

For example, Project or Aggregate introduce their own scopes semantically, so that a lower resolution can lookup correlated names:

CREATE TABLE IF NOT EXISTS t1 (col1 INT, col2 STRING);
CREATE TABLE IF NOT EXISTS t2 (col1 INT, col2 STRING);

-- Here we need a scope for the upper [[Project]], and a separate scope for the correlated
-- subquery, because its [[Filter]] need to lookup `t1.col1` from the upper scope.
-- Those scopes have to be independent to avoid polluting each other's attributes.
SELECT col1, (SELECT col2 FROM t2 WHERE t2.col1 == t1.col1 LIMIT 1) FROM t1;

Also, we need separate scopes for the operators with multiple children, so that the next child's resolution wouldn't try to work with the data from it's sibling's scope, to avoid all kinds of undefined behavior:

val resolvedLeftChild = withNewScope {
   resolve(unresolvedExcept.left)
}

// Right child should not see the left child's resolution data to avoid subtle bugs, so we
// create a fresh scope here.

val resolvedRightChild = withNewScope {
   resolve(unresolvedExcept.right)
}

Sets all SQL configurations specified in pairs, calls f, and then restores all SQL configurations.