/**
* Derives the list of column names suitable for NATURAL JOIN. These are the columns that occur
* exactly once on each side of the join.
*
* @param leftRowType Row type of left input to the join
* @param rightRowType Row type of right input to the join
* @return List of columns that occur once on each side
*/
public static List<String> deriveNaturalJoinColumnList(
RelDataType leftRowType, RelDataType rightRowType) {
List<String> naturalColumnNames = new ArrayList<String>();
final List<String> leftNames = leftRowType.getFieldNames();
final List<String> rightNames = rightRowType.getFieldNames();
for (String name : leftNames) {
if ((Collections.frequency(leftNames, name) == 1)
&& (Collections.frequency(rightNames, name) == 1)) {
naturalColumnNames.add(name);
}
}
return naturalColumnNames;
}
public static RelDataType createTypeFromProjection(
RelDataType type,
List<String> columnNameList,
RelDataTypeFactory typeFactory,
boolean caseSensitive) {
// If the names in columnNameList and type have case-sensitive differences,
// the resulting type will use those from type. These are presumably more
// canonical.
final List<RelDataTypeField> fields = new ArrayList<RelDataTypeField>(columnNameList.size());
for (String name : columnNameList) {
RelDataTypeField field = type.getField(name, caseSensitive);
fields.add(type.getFieldList().get(field.getIndex()));
}
return typeFactory.createStructType(fields);
}
public static void checkCharsetAndCollateConsistentIfCharType(RelDataType type) {
// (every charset must have a default collation)
if (SqlTypeUtil.inCharFamily(type)) {
Charset strCharset = type.getCharset();
Charset colCharset = type.getCollation().getCharset();
assert null != strCharset;
assert null != colCharset;
if (!strCharset.equals(colCharset)) {
if (false) {
// todo: enable this checking when we have a charset to
// collation mapping
throw new Error(
type.toString()
+ " was found to have charset '"
+ strCharset.name()
+ "' and a mismatched collation charset '"
+ colCharset.name()
+ "'");
}
}
}
}
/**
* Looks up a field with a given name, returning null if not found.
*
* @param rowType Row type
* @param columnName Field name
* @return Field, or null if not found
*/
public static RelDataTypeField lookupField(
boolean caseSensitive, final RelDataType rowType, String columnName) {
RelDataTypeField field = rowType.getField(columnName, caseSensitive);
if (field != null) {
return field;
}
// If record type is flagged as having "any field you ask for",
// return a type. (TODO: Better way to mark accommodating types.)
RelDataTypeField extra = RelDataTypeImpl.extra(rowType);
if (extra != null) {
return new RelDataTypeFieldImpl(columnName, -1, extra.getType());
}
return null;
}
/**
* Returns the "extra" field in a row type whose presence signals that fields will come into
* existence just by asking for them.
*
* @param rowType Row type
* @return The "extra" field, or null
*/
public static RelDataTypeField extra(RelDataType rowType) {
// Even in a case-insensitive connection, the name must be precisely
// "_extra".
return rowType.getField("_extra", true);
}
/**
* Returns true if a type is a simple cast of another type. It is if the cast type is nullable and
* the cast is one of the following:
* <li>x TO x
* <li>char(n) TO varchar(m)
* <li>varchar(n) TO varchar(m)
* <li>x not null TO x nullable
*
* @param origType original type passed into the cast operand
* @param castType type the operand will be casted to
* @return true if the cast is simple
*/
private boolean isCastSimple(RelDataType origType, RelDataType castType) {
SqlTypeName origTypeName = origType.getSqlTypeName();
SqlTypeName castTypeName = castType.getSqlTypeName();
if (!(castType.isNullable())) {
return false;
}
Charset origCharset = origType.getCharset();
Charset castCharset = castType.getCharset();
if ((origCharset != null) || (castCharset != null)) {
if ((origCharset == null) || (castCharset == null)) {
return false;
}
if (!origCharset.equals(castCharset)) {
return false;
}
}
return ((origType == castType)
|| ((origTypeName == SqlTypeName.CHAR) && (castTypeName == SqlTypeName.VARCHAR))
|| ((origTypeName == SqlTypeName.VARCHAR) && (castTypeName == SqlTypeName.VARCHAR))
|| ((origTypeName == castTypeName)
&& (origType.getPrecision() == castType.getPrecision())
&& ((origTypeName != SqlTypeName.DECIMAL)
|| (origType.getScale() == castType.getScale()))
&& (!origType.isNullable() && castType.isNullable())));
}