gudusoft.gsqlparser.nodes.flink

Class TFlinkWatermarkClause

Object

gudusoft.gsqlparser.nodes.TParseTreeNode

gudusoft.gsqlparser.nodes.flink.TFlinkWatermarkClause

All Implemented Interfaces:

Visitable, Iterator<TSourceToken>

public class TFlinkWatermarkClause
extends TParseTreeNode

Represents Flink's WATERMARK clause for event-time processing.

The WATERMARK clause defines watermark generation strategies for event-time processing in Flink SQL. It specifies which column represents event time and the watermark strategy expression.

Syntax:

 WATERMARK FOR rowtime_column AS watermark_strategy_expression
 

Requirements:

• The rowtime_column must be an existing column of type TIMESTAMP(3)
• The watermark_strategy_expression must return TIMESTAMP(3)
• Watermarks must only emit non-null values larger than previously emitted ones

Common Strategies:

• Strictly ascending: WATERMARK FOR order_time AS order_time
• Ascending (1ms tolerance): WATERMARK FOR order_time AS order_time - INTERVAL '0.001' SECOND
• Bounded delay: WATERMARK FOR order_time AS order_time - INTERVAL '5' SECOND

Example:

 CREATE TABLE Orders (
     `user` BIGINT,
     product STRING,
     order_time TIMESTAMP(3),
     WATERMARK FOR order_time AS order_time - INTERVAL '5' SECOND
 ) WITH (
     'connector' = 'kafka',
     'topic' = 'orders'
 );
 

See Also:

Flink SQL CREATE TABLE

Field Summary

Fields inherited from class gudusoft.gsqlparser.nodes.TParseTreeNode

dbvendor, doubleLinkedTokenListToString, nodeActionAppend, nodeActionInsert, nodeActionRemove, nodeActionUnknown, nodeActionUpdate, nodeActionUpdateText, nodeChangeEndToken, nodeChangeStartToken

Constructor Summary

Constructors

Constructor and Description
TFlinkWatermarkClause()

Method Summary

Modifier and Type	Method and Description
void	accept(TParseTreeVisitor v) Accept a visitor
void	acceptChildren(TParseTreeVisitor v) Accept a visitor to iterate this class and sub-nodes of this class
TObjectName	getEventTimeColumn() Get the event time column name.
String	getEventTimeColumnName() Get the event time column name as a string.
TExpression	getWatermarkExpression() Get the watermark strategy expression.
void	init(Object arg1, Object arg2) Initialize with event time column and watermark expression.
void	setEventTimeColumn(TObjectName eventTimeColumn) Set the event time column name.
void	setWatermarkExpression(TExpression watermarkExpression) Set the watermark strategy expression.

Methods inherited from class gudusoft.gsqlparser.nodes.TParseTreeNode

addAllMyTokensToTokenList, addToTokenChain, appendNewNode, calculateTokenCount, doAppendNewNode, doParse, fastSetString, getAnchorNode, getColumnNo, getCommentAfterNode, getCommentBeforeNode, getCompactString, getDummyTag, getEndToken, getEvaluateDatatype, getEvalValue, getGsqlparser, getLineNo, getLocation, getMd5, getNodeStatus, getNodeType, getParentObjectName, getPlainText, getStartToken, getTokenCount, hasNext, init, init, init, init, init, init, init, init, init, insertAfterAToken, insertNewNodeBeforeMe, isChanged, isTokensInChain, next, refreshAllNodesTokenCount, remove, removeAllMyTokensFromTokenList, removeTokens, removeTokensBetweenNodes, removeTokensBetweenToken, replaceWithNewNode, resetIterator, setAnchorNode, setChanged, setDummyTag, setEndToken, setEndToken, setEndToken, setEndToken, setEndToken, setEndTokenDirectly, setEvaluateDatatype, setEvalValue, setGsqlparser, setIncludingComment, setLocation, setNewSubNode, setNodeStatus, setNodeType, setParent, setPlainText, setStartToken, setStartToken, setStartToken, setStartToken, setStartTokenDirectly, setString, setString2, subNodeInNode, toScript, toString, toString2

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface Iterator

forEachRemaining

Constructor Detail

TFlinkWatermarkClause

public TFlinkWatermarkClause()

Method Detail

init

public void init(Object arg1,
                 Object arg2)

Initialize with event time column and watermark expression.

Overrides:

init in class TParseTreeNode

Parameters:

arg1 - the event time column name (TObjectName)

arg2 - the watermark strategy expression (TExpression)

getEventTimeColumn

public TObjectName getEventTimeColumn()

Get the event time column name.

This is the column that Flink uses as the event time attribute. It must be of type TIMESTAMP(3).

Returns:

the event time column name

setEventTimeColumn

public void setEventTimeColumn(TObjectName eventTimeColumn)

Set the event time column name.

Parameters:

eventTimeColumn - the event time column name

getWatermarkExpression

public TExpression getWatermarkExpression()

Get the watermark strategy expression.

This expression defines how watermarks are generated. Common patterns include:

• Strictly ascending: just the column name (e.g., order_time)
• Bounded out-of-orderness: column minus interval (e.g., order_time - INTERVAL '5' SECOND)

Returns:

the watermark strategy expression

setWatermarkExpression

public void setWatermarkExpression(TExpression watermarkExpression)

Set the watermark strategy expression.

Parameters:

watermarkExpression - the watermark strategy expression

getEventTimeColumnName

public String getEventTimeColumnName()

Get the event time column name as a string.

Returns:

the column name string, or null if not set

accept

public void accept(TParseTreeVisitor v)

Description copied from class: TParseTreeNode

Accept a visitor

Specified by:

accept in interface Visitable

Overrides:

accept in class TParseTreeNode

Parameters:

v - visitor is a descendant class of TParseTreeVisitor

acceptChildren

public void acceptChildren(TParseTreeVisitor v)

Description copied from class: TParseTreeNode

Accept a visitor to iterate this class and sub-nodes of this class

Specified by:

acceptChildren in interface Visitable

Overrides:

acceptChildren in class TParseTreeNode

Parameters:

v - visitor is a descendant class of TParseTreeVisitor