/**
* Resolves a multi-part identifier such as "SCHEMA.EMP.EMPNO" to a namespace. The returned
* namespace may represent a schema, table, column, etc.
*
* @pre names.size() > 0
* @post return != null
*/
public static SqlValidatorNamespace lookup(SqlValidatorScope scope, List<String> names) {
Util.pre(names.size() > 0, "names.size() > 0");
SqlValidatorNamespace namespace = null;
for (int i = 0; i < names.size(); i++) {
String name = names.get(i);
if (i == 0) {
namespace = scope.resolve(name, null, null);
} else {
namespace = namespace.lookupChild(name);
}
}
Util.permAssert(namespace != null, "post: namespace != null");
return namespace;
}
/**
* Converts a {@link SqlValidatorScope} into a {@link RelOptTable}. This is only possible if the
* scope represents an identifier, such as "sales.emp". Otherwise, returns null.
*
* @param namespace Namespace
* @param catalogReader Schema
* @param datasetName Name of sample dataset to substitute, or null to use the regular table
* @param usedDataset Output parameter which is set to true if a sample dataset is found; may be
* null
*/
public static RelOptTable getRelOptTable(
SqlValidatorNamespace namespace,
Prepare.CatalogReader catalogReader,
String datasetName,
boolean[] usedDataset) {
if (namespace.isWrapperFor(IdentifierNamespace.class)) {
IdentifierNamespace identifierNamespace = namespace.unwrap(IdentifierNamespace.class);
final List<String> names = identifierNamespace.getId().names;
if ((datasetName != null) && (catalogReader instanceof RelOptSchemaWithSampling)) {
return ((RelOptSchemaWithSampling) catalogReader)
.getTableForMember(names, datasetName, usedDataset);
} else {
// Schema does not support substitution. Ignore the dataset,
// if any.
return catalogReader.getTableForMember(names);
}
} else {
return null;
}
}