Hi,
关于你举的例子，如果编译了源码的话，可以在FlinkSqlParserImpl这个被动态生成的词法解析器类中找到PostfixRowOperator方法，大致是通过识别到IS
NOT NULL这三个关键字，转化为Calcite的这个内置函数SqlStdOperatorTable.IS_NOT_NULL
--
Best！
Xuyang
在 2023-11-24 15:15:04，"jinzhuguang" <jinzhuguan...@163.com> 写道：
>flink 1.18.0
>
>
>例如我写下一条SQL：
> select * from KafkaTable where id is not null;
>
>IS NOT NULL应该属于系统内建函数，于是我找到相关代码：
>
>public static final BuiltInFunctionDefinition IS_NOT_NULL =
> BuiltInFunctionDefinition.newBuilder()
> .name("isNotNull")
> .kind(SCALAR)
>
> .inputTypeStrategy(wildcardWithCount(ConstantArgumentCount.of(1)))
>
> .outputTypeStrategy(explicit(DataTypes.BOOLEAN().notNull()))
> .build();
>
>发现他的name是“ isNotNull”，和“is not null”对应不上。并且经过实际测验，确实证实了我的猜想：
>
>DEBUG org.apache.flink.table.module.ModuleManager [] - Cannot
>find FunctionDefinition 'is not null' from any loaded modules.
>
>
>所以我很疑惑，SQL到底是在哪里找到了”is not null”这个函数的呢？
>
>以下是调用栈：
>@org.apache.flink.table.planner.catalog.FunctionCatalogOperatorTable.lookupOperatorOverloads()
> at
> org.apache.calcite.sql.util.ChainedSqlOperatorTable.lookupOperatorOverloads(ChainedSqlOperatorTable.java:69)
> at
> org.apache.calcite.sql.SqlUtil.lookupSubjectRoutinesByName(SqlUtil.java:609)
> at
> org.apache.calcite.sql.SqlUtil.lookupSubjectRoutines(SqlUtil.java:535)
> at org.apache.calcite.sql.SqlUtil.lookupRoutine(SqlUtil.java:486)
> at org.apache.calcite.sql.SqlOperator.deriveType(SqlOperator.java:595)
> at
> org.apache.calcite.sql.validate.SqlValidatorImpl$DeriveTypeVisitor.visit(SqlValidatorImpl.java:6302)
> at
> org.apache.calcite.sql.validate.SqlValidatorImpl$DeriveTypeVisitor.visit(SqlValidatorImpl.java:6287)
> at org.apache.calcite.sql.SqlCall.accept(SqlCall.java:161)
> at
> org.apache.calcite.sql.validate.SqlValidatorImpl.deriveTypeImpl(SqlValidatorImpl.java:1869)
> at
> org.apache.calcite.sql.validate.SqlValidatorImpl.deriveType(SqlValidatorImpl.java:1860)
> at
> org.apache.calcite.sql.validate.SqlValidatorImpl.validateWhereOrOn(SqlValidatorImpl.java:4341)
> at
> org.apache.calcite.sql.validate.SqlValidatorImpl.validateWhereClause(SqlValidatorImpl.java:4333)
> at
> org.apache.calcite.sql.validate.SqlValidatorImpl.validateSelect(SqlValidatorImpl.java:3606)
> at
> org.apache.calcite.sql.validate.SelectNamespace.validateImpl(SelectNamespace.java:64)
> at
> org.apache.calcite.sql.validate.AbstractNamespace.validate(AbstractNamespace.java:89)
> at
> org.apache.calcite.sql.validate.SqlValidatorImpl.validateNamespace(SqlValidatorImpl.java:1050)
> at
> org.apache.calcite.sql.validate.SqlValidatorImpl.validateQuery(SqlValidatorImpl.java:1025)
> at org.apache.calcite.sql.SqlSelect.validate(SqlSelect.java:248)
> at
> org.apache.calcite.sql.validate.SqlValidatorImpl.validateScopedExpression(SqlValidatorImpl.java:1000)
> at
> org.apache.calcite.sql.validate.SqlValidatorImpl.validate(SqlValidatorImpl.java:749)
> at
> org.apache.flink.table.planner.calcite.FlinkPlannerImpl.org$apache$flink$table$planner$calcite$FlinkPlannerImpl$$validate(FlinkPlannerImpl.scala:196)
> at
> org.apache.flink.table.planner.calcite.FlinkPlannerImpl.validate(FlinkPlannerImpl.scala:117)
> at
> org.apache.flink.table.planner.operations.SqlNodeToOperationConversion.convert(SqlNodeToOperationConversion.java:261)
> at
> org.apache.flink.table.planner.delegation.ParserImpl.parse(ParserImpl.java:106)
> at
> org.apache.flink.table.gateway.service.operation.OperationExecutor.executeStatement(OperationExecutor.java:187)
> at
> org.apache.flink.table.gateway.service.SqlGatewayServiceImpl.lambda$executeStatement$1(SqlGatewayServiceImpl.java:212)
> at
> org.apache.flink.table.gateway.service.operation.OperationManager.lambda$submitOperation$1(OperationManager.java:119)
> at
> org.apache.flink.table.gateway.service.operation.OperationManager$Operation.lambda$run$0(OperationManager.java:258)
> at
> java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
> at java.util.concurrent.FutureTask.run(FutureTask.java:266)
> at
> java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
> at java.util.concurrent.FutureTask.run(FutureTask.java:266)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
> at java.lang.Thread.run(Thread.java:750)
