/**
* Constructs a FarragoReentrantSubquery.
*
* @param subq the subquery to evaluate
* @param parentConverter sqlToRelConverter associated with the parent query
* @param isExists whether the subquery is part of an EXISTS expression
* @param isExplain whether the subquery is part of an EXPLAIN PLAN statement
* @param results the resulting evaluated expressions
*/
FarragoReentrantSubquery(
SqlCall subq,
SqlToRelConverter parentConverter,
boolean isExists,
boolean isExplain,
List<RexNode> results) {
super(
FennelRelUtil.getPreparingStmt(parentConverter.getCluster()).getRootStmtContext(),
parentConverter.getRexBuilder(),
results);
FarragoSessionStmtContext rootContext = getRootStmtContext();
if (rootContext != null) {
rootContext.setSaveFirstTxnCsn();
}
if (!isExists) {
assert subq.getKind() == SqlKind.SCALAR_QUERY;
}
this.subq = subq;
this.parentConverter = parentConverter;
this.isExists = isExists;
this.isExplain = isExplain;
}
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);
}
}
}
}