Calcite SQL 解析、语法扩展、元数据验证原理与实战（上）

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-dependency-plugin</artifactId>
    <executions>
        <execution>
            <id>unpack-parser-template</id>
            <phase>initialize</phase>
            <goals>
                <goal>unpack</goal>
            </goals>
            <configuration>
                <artifactItems>
                    <artifactItem>
                        <groupId>org.apache.calcite</groupId>
                        <artifactId>calcite-core</artifactId>
                        <version>1.31.0</version>
                        <type>jar</type>
                        <overWrite>true</overWrite>
                        <outputDirectory>${project.build.directory}/</outputDirectory>
                        <includes>**/Parser.jj</includes>
                    </artifactItem>
                </artifactItems>
                <skip>false</skip>
            </configuration>
        </execution>
    </executions>
</plugin>

/*为了演示方便 SQL语法有所简化*/
CREATE MATERIALIZED VIEW
[ IF NOT EXISTS ] view_name
AS query

public class CreateMaterializedView
        extends SqlCall
{
    public static final SqlSpecialOperator CREATE_MATERIALIZED_VIEW = new SqlSpecialOperator("CREATE_MATERIALIZED_VIEW", SqlKind.OTHER_DDL);
    SqlIdentifier viewName;
    boolean existenceCheck;
    SqlSelect query;

    public CreateMaterializedView(SqlParserPos pos, SqlIdentifier viewName, boolean existenceCheck, SqlSelect query)
{
        super(pos);
        this.viewName = viewName;
        this.existenceCheck = existenceCheck;
        this.query = query;
    }

    @Override
    public SqlOperator getOperator()
{
        return CREATE_MATERIALIZED_VIEW;
    }

    @Override
    public List<SqlNode> getOperandList()
{
        List<SqlNode> operands = new ArrayList<>();
        operands.add(viewName);
        operands.add(SqlLiteral.createBoolean(existenceCheck, SqlParserPos.ZERO));
        operands.add(query);
        return operands;
    }

    @Override
    public void unparse(SqlWriter writer, int leftPrec, int rightPrec)
{
        writer.keyword("CREATE MATERIALIZED VIEW");
        if (existenceCheck) {
            writer.keyword("IF NOT EXISTS");
        }
        viewName.unparse(writer, leftPrec, rightPrec);
        writer.keyword("AS");
        query.unparse(writer, leftPrec, rightPrec);
    }
}

SqlNode SqlCreateMaterializedView() :
{
    SqlParserPos pos;
    SqlIdentifier viewName;
    boolean existenceCheck = false;
    SqlSelect query;
}
{
    <CREATE> { pos = getPos(); }
    <MATERIALIZED> <VIEW>
    <#-- [] 代表里面的元素可能出现 -->
        [ <IF> <NOT> <EXISTS> { existenceCheck = true; } ]
    <#-- CompoundIdentifier() 为 Calcite 内置函数，
    可以解析类似 catalog.schema.tableName 这样的全路径表示形式 -->
    viewName = CompoundIdentifier()
    <AS>
    <#-- SqlSelect() 为 Calcite 内置函数，解析一个 select sql -->
    query = SqlSelect()
    {
        return new CreateMaterializedView(pos, viewName, existenceCheck, query);
    }
}

data: {
  parser: {
    package: "com.aloudata.demo.parser.impl",
    class: "DemoSqlParserImpl",

    imports: [
        "com.aloudata.tardis.parser.CreateMaterializedView.CreateType"
    ]

    keywords: [
        "IF",
        "MATERIALIZED"
    ]

    statementParserMethods: [
        "SqlCreateMaterializedView()"
    ]

    implementationFiles: [
        "parserImpls.ftl"
    ]
  }
}

freemarkerLinks: {
  includes: includes/
}

<plugin>
      <groupId>com.googlecode.fmpp-maven-plugin</groupId>
      <artifactId>fmpp-maven-plugin</artifactId>
      <version>1.0</version>
      <configuration>
          <cfgFile>src/main/codegen/config.fmpp</cfgFile>
          <outputDirectory>target/generated-sources/fmpp<outputDirectory>
          <templateDirectory>${project.build.directory}/codegen/templates</templateDirectory>
      </configuration>
    <dependencies>
        <dependency>
            <groupId>org.freemarker</groupId>
            <artifactId>freemarker</artifactId>
            <version>2.3.28</version>
        </dependency>
    </dependencies>
    <executions>
        <execution>
            <id>generate-fmpp-sources</id>
            <phase>generate-sources</phase>
            <goals>
                <goal>generate</goal>
            </goals>
        </execution>
    </executions>
</plugin>

<plugin> <!-- generate the parser (Parser.jj is itself generated wit fmpp above) -->
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>javacc-maven-plugin</artifactId>
    <version>2.6</version>
    <executions>
        <execution>
            <id>javacc</id>
            <phase>generate-sources</phase>
            <goals><goal>javacc</goal></goals>
            <configuration>
                <sourceDirectory>${project.build.directory}/generated-sources/fmpp</sourceDirectory>
                <includes>
                    <include>**/*.jj</include>
                </includes>
                <lookAhead>1</lookAhead>
                <isStatic>false</isStatic>
                <outputDirectory>${project.build.directory}/generated-sources/javacc</outputDirectory>
            </configuration>
        </execution>
    </executions>
</plugin>

@Test
    public void test() throws SqlParseException {
        String sql = "CREATE MATERIALIZED VIEW IF NOT EXISTS "test"."demo"."materializationName" AS SELECT * FROM "system"";

        SqlParser.Config myConfig = SqlParser.config()
                .withQuoting(Quoting.DOUBLE_QUOTE)
                .withQuotedCasing(Casing.UNCHANGED)
                .withParserFactory(DemoSqlParserImpl.FACTORY);
        SqlParser parser = SqlParser.create(sql, myConfig);
        SqlNode sqlNode = parser.parseQuery();
        assertTrue(sqlNode instanceof CreateMaterializedView);
        System.out.println(sqlNode);
    }

S –> AB
A –> aA | ε   // ε 代表一个空字符
B –> b |

<configuration>
  <lookAhead>2</lookAhead>
</configuration>

SqlNode SqlCreateMaterializedView() :
{
    ...
}
{
    LOOKAHEAD(2)
    ...
}