DefaultKsqlParser¶

DefaultKsqlParser is a KsqlParser.

Demo¶

import io.confluent.ksql.parser.DefaultKsqlParser
val parser = new DefaultKsqlParser()

val ksql = "SELECT * FROM my_stream;"
val statements = parser.parse(ksql)

import scala.jdk.CollectionConverters._
val pstmt = statements.asScala.head
assert(pstmt.isInstanceOf[io.confluent.ksql.parser.KsqlParser.ParsedStatement])

Creating Instance¶

DefaultKsqlParser takes no arguments to be created.

DefaultKsqlParser is created when:

Cli is created
EngineContext utility is used to create an EngineContext and createSandbox
KsqlResource is requested for TERMINATE_CLUSTER

Parsing SQL Statements (parse)¶

List<ParsedStatement> parse(
  String sql)

parse parses the given sql (using ANTLR) and creates as many ParsedStatements as there are SQL statements in the sql.

ANTLR

This is when a SQL text is parsed (transformed) using ANTLR into a collection of ksqlDB's ParsedStatements according to the SqlBase.g4 grammar:

statements
    : (singleStatement)* EOF
    ;

Every ParsedStatements maps exactly to a singleStatement.

parse is part of the KsqlParser abstraction.

Preparing Statement for Execution¶

PreparedStatement<?> prepare(
  ParsedStatement stmt,
  TypeRegistry typeRegistry)

prepare is part of the KsqlParser abstraction.

prepare creates an AstBuilder (with the given TypeRegistry) to build a Statement.

In the end, prepare creates a PreparedStatement (with the KSQL statement in text format and the Statement).