/**
* Creates projection list for scan. If the projection contains expressions, then the input
* references from those expressions are extracted and that list of references becomes the
* projection list.
*
* @param origScan row scan underneath the project
* @param projRel ProjectRel that we will be creating the projection for
* @param projectedColumns returns a list of the projected column ordinals, if it is possible to
* project
* @param preserveExprCondition condition that identifies special expressions that should be
* preserved in the projection
* @param defaultExpr expression to be used in the projection if no fields or special columns are
* selected
* @param newProjList returns a new projection RelNode corresponding to a projection that now
* references a rowscan that is projecting the input references that were extracted from the
* original projection expressions; if the original expression didn't contain expressions,
* then this list is returned empty
* @return true if columns in projection list from the scan need to be renamed
*/
public boolean createProjectionList(
FennelRel origScan,
ProjectRel projRel,
List<Integer> projectedColumns,
PushProjector.ExprCondition preserveExprCondition,
RexNode defaultExpr,
List<ProjectRel> newProjList) {
// REVIEW: what about AnonFields?
int n = projRel.getChildExps().length;
RelDataType rowType = origScan.getRowType();
RelDataType projType = projRel.getRowType();
RelDataTypeField[] projFields = projType.getFields();
List<Integer> tempProjList = new ArrayList<Integer>();
boolean needRename = false;
for (int i = 0; i < n; ++i) {
RexNode exp = projRel.getChildExps()[i];
List<String> origFieldName = new ArrayList<String>();
Integer projIndex = mapProjCol(exp, origFieldName, rowType);
if (projIndex == null) {
// there are expressions in the projection; we need to extract
// all input references and any special expressions from the
// projection
PushProjector pushProject =
new PushProjector(projRel, null, origScan, preserveExprCondition);
ProjectRel newProject = pushProject.convertProject(defaultExpr);
if (newProject == null) {
// can't do any further projection
return false;
}
newProjList.add(newProject);
// using the input references we just extracted, it should now
// be possible to create a projection for the row scan
needRename =
createProjectionList(
origScan,
(ProjectRel) newProject.getChild(),
projectedColumns,
preserveExprCondition,
defaultExpr,
newProjList);
assert (projectedColumns.size() > 0);
return needRename;
}
String projFieldName = projFields[i].getName();
if (!projFieldName.equals(origFieldName.get(0))) {
needRename = true;
}
tempProjList.add(projIndex);
}
// now that we've determined it is possible to project, add the
// ordinals to the return list
projectedColumns.addAll(tempProjList);
return needRename;
}
protected Integer mapFieldRef(RexNode exp, List<String> origFieldName, RelDataType rowType) {
RexInputRef fieldAccess = (RexInputRef) exp;
origFieldName.add(rowType.getFields()[fieldAccess.getIndex()].getName());
return fieldAccess.getIndex();
}
protected void executeImpl() throws Exception {
SqlCall call = (SqlCall) subq;
SqlSelect select = (SqlSelect) call.getOperands()[0];
// Convert the SqlNode tree to a RelNode tree; we need to do this
// here so the RelNode tree is associated with the new preparing
// stmt.
FarragoPreparingStmt preparingStmt = (FarragoPreparingStmt) getPreparingStmt();
SqlValidator validator = preparingStmt.getSqlValidator();
SqlToRelConverter sqlConverter = preparingStmt.getSqlToRelConverter(validator, preparingStmt);
preparingStmt.setParentStmt(FennelRelUtil.getPreparingStmt(parentConverter.getCluster()));
// Add to the new converter any subqueries that have already been
// converted by the parent so we can avoid re-executing them
sqlConverter.addConvertedNonCorrSubqs(parentConverter.getMapConvertedNonCorrSubqs());
RelNode plan = sqlConverter.convertQuery(select, true, true);
// The subquery cannot have dynamic parameters
if (sqlConverter.getDynamicParamCount() > 0) {
failed = true;
return;
}
List<RexNode> exprs = new ArrayList<RexNode>();
RelDataType resultType = null;
if (!isExists) {
// Non-EXISTS subqueries need to be converted to single-value
// subqueries
plan = sqlConverter.convertToSingleValueSubq(select, plan);
// Create a dummy expression to store the type of the result.
// When setting the type, derive the type based on what a
// scalar subquery should return and create the type from the
// type factory of the parent query.
resultType = call.getOperator().deriveType(validator, validator.getFromScope(select), call);
resultType = rexBuilder.getTypeFactory().copyType(resultType);
exprs.add(rexBuilder.makeInputRef(resultType, 0));
}
plan = sqlConverter.decorrelate(select, plan);
// If the subquery is part of an EXPLAIN PLAN statement, don't
// execute the subquery, but instead just return a dynamic parameter
// as a placeholder for the subquery result. Otherwise, execute
// the query to produce the constant expression. Cast the expression
// as needed so the type matches the expected result type.
RexNode constExpr;
if (isExplain) {
if (isExists) {
resultType = rexBuilder.getTypeFactory().createSqlType(SqlTypeName.BOOLEAN);
}
constExpr =
rexBuilder.makeDynamicParam(
resultType, parentConverter.getDynamicParamCountInExplain(true));
results.add(constExpr);
} else {
executePlan(plan, exprs, isExists, false);
if (!failed && !isExists) {
constExpr = results.get(0);
if (constExpr.getType() != resultType) {
constExpr = rexBuilder.makeCast(resultType, constExpr);
results.set(0, constExpr);
}
}
}
}