amaliujia commented on a change in pull request #1761: URL: https://github.com/apache/calcite/pull/1761#discussion_r414350668
########## File path: core/src/main/java/org/apache/calcite/sql/SqlSessionTableFunction.java ########## @@ -0,0 +1,71 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to you under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.calcite.sql; + +import org.apache.calcite.rel.type.RelDataType; +import org.apache.calcite.sql.type.SqlOperandCountRanges; +import org.apache.calcite.sql.type.SqlTypeName; +import org.apache.calcite.sql.type.SqlTypeUtil; +import org.apache.calcite.sql.validate.SqlValidator; + +/** + * SqlSessionTableFunction implements an operator for per-key sessionization. It allows + * four parameters: + * 1. a table. + * 2. a descriptor to provide a watermarked column name from the input table. + * 3. a descriptor to provide a column as key, on which sessionization will be applied. + * 4. an interval parameter to specify a inactive activity gap to break sessions. + */ +public class SqlSessionTableFunction extends SqlWindowTableFunction { + public SqlSessionTableFunction() { + super(SqlKind.SESSION.name()); + } + + @Override public SqlOperandCountRange getOperandCountRange() { + return SqlOperandCountRanges.of(4); + } + + @Override public boolean checkOperandTypes(SqlCallBinding callBinding, + boolean throwOnFailure) { + final SqlNode operand0 = callBinding.operand(0); + final SqlValidator validator = callBinding.getValidator(); + final RelDataType type = validator.getValidatedNodeType(operand0); + if (type.getSqlTypeName() != SqlTypeName.ROW) { + return throwValidationSignatureErrorOrReturnFalse(callBinding, throwOnFailure); + } + final SqlNode operand1 = callBinding.operand(1); + if (operand1.getKind() != SqlKind.DESCRIPTOR) { + return throwValidationSignatureErrorOrReturnFalse(callBinding, throwOnFailure); + } + validateColumnNames(validator, type.getFieldNames(), ((SqlCall) operand1).getOperandList()); + final SqlNode operand2 = callBinding.operand(2); + if (operand2.getKind() != SqlKind.DESCRIPTOR) { + return throwValidationSignatureErrorOrReturnFalse(callBinding, throwOnFailure); + } + validateColumnNames(validator, type.getFieldNames(), ((SqlCall) operand2).getOperandList()); + final RelDataType type3 = validator.getValidatedNodeType(callBinding.operand(3)); + if (!SqlTypeUtil.isInterval(type3)) { + return throwValidationSignatureErrorOrReturnFalse(callBinding, throwOnFailure); + } + return true; + } + + @Override public String getAllowedSignatures(String opNameToUse) { + return getName() + "(TABLE table_name, DESCRIPTOR(col), " + + "DESCRIPTOR(col), datetime interval)"; Review comment: In fact, `DESCRIPTOR` is a part of `SQL standard 2016: Polymorphic table functions` (https://issues.apache.org/jira/browse/CALCITE-2270). `DESCRIPTOR` is designed to specify columns explicitly in table functions. That was one of the purpose it was created for. You can find a free copy of `SQL standard 2016: Polymorphic table functions` in this link: https://modern-sql.com/standard ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
