在Flink Table SQL中，带引号的标识符可以使用什么语法？

问题描述

我试图在Flink中使用带引号的标识符（主要是因为我有一些与year之类的关键字冲突的列名）。但是我无法解析。

我归纳为一个最小的失败示例：

EnvironmentSettings settings = 
EnvironmentSettings.newInstance().useBlinkPlanner().inBatchMode().build();
TableEnvironment tEnv = TableEnvironment.create(settings);
 String sql = "CREATE TABLE table1(\"ts\" TIMESTAMP) WITH ('connector' = 'filesystem','path' = 'file:///Users/ecerulm/tmp/csv/','format' = 'csv');";
System.out.println(sql);
tEnv.executesql(sql);

未能抱怨"ts"部分：

org.apache.flink.table.api.sqlParserException: sql parse Failed. Encountered "\"" at line 1,column 21.
Was expecting one of:
    "CONSTRAINT" ...
    "PRIMARY" ...
    "UNIQUE" ...
    "WATERMARK" ...
    <BRACKET_QUOTED_IDENTIFIER> ...
    <QUOTED_IDENTIFIER> ...
    <BACK_QUOTED_IDENTIFIER> ...
    <HYPHENATED_IDENTIFIER> ...
    <IDENTIFIER> ...
    <UNICODE_QUOTED_IDENTIFIER> ...
    

    at org.apache.flink.table.planner.calcite.CalciteParser.parse(CalciteParser.java:56)
    at org.apache.flink.table.planner.delegation.ParserImpl.parse(ParserImpl.java:76)
    at org.apache.flink.table.api.internal.TableEnvironmentImpl.executesql(TableEnvironmentImpl.java:658)
    at com.rubenlaguna.BatchJobTest.testBatchJob(BatchJobTest.java:22)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runchild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runchild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runchildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:220)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:53)

据我从异常中了解到，它不期望使用"字符，因为它与<QUOTED_IDENTIFIER>之类的任何解析选项都不匹配，但据我从Calcite documentation所理解的，引用的标识符的语法只是"myidentifier"。

解决方法

Flink documentation for Expanding Table Identifiers说：

标识符遵循SQL要求，这意味着可以使用反引号（`）对其进行转义。

它没有不提及双引号标识符。

因此，尽管Flink SQL基于Calcite SQL，尽管Calcite has double quoted identifiers似乎Flink SQL仅支持常规sql标识符+反引号标识符。因此，您将需要编写如下查询：

String sql = "CREATE TABLE table1(`ts` TIMESTAMP) WITH ('connector' = 'filesystem','path' = 'file:///Users/ecerulm/tmp/csv/','format' = 'csv')";
tEnv.executeSql(sql);

因此，使用"ts"（带反引号）代替`ts`（带双引号）。