org.apache.flink.table.planner.functions.aggfunctions.LeadLagAggFunction Maven / Gradle / Ivy
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* to you under the Apache License, Version 2.0 (the
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*
* http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.flink.table.planner.functions.aggfunctions;
import org.apache.flink.table.api.DataTypes;
import org.apache.flink.table.expressions.Expression;
import org.apache.flink.table.expressions.UnresolvedReferenceExpression;
import org.apache.flink.table.runtime.operators.over.frame.OffsetOverFrame;
import org.apache.flink.table.types.DataType;
import org.apache.flink.table.types.logical.DecimalType;
import org.apache.flink.table.types.logical.TimeType;
import org.apache.flink.table.types.logical.TimestampType;
import static org.apache.flink.table.expressions.ApiExpressionUtils.unresolvedRef;
import static org.apache.flink.table.planner.expressions.ExpressionBuilder.cast;
import static org.apache.flink.table.planner.expressions.ExpressionBuilder.literal;
import static org.apache.flink.table.planner.expressions.ExpressionBuilder.typeLiteral;
/**
* LEAD and LAG aggregate functions return the value of given expression evaluated at given offset.
* The functions only are used by over window.
*
* LAG(input, offset, default) - Returns the value of `input` at the `offset`th row before the
* current row in the window. The default value of `offset` is 1 and the default value of `default`
* is null. If the value of `input` at the `offset`th row is null, null is returned. If there is no
* such offset row (e.g., when the offset is 1, the first row of the window does not have any
* previous row), `default` is returned.
*
*
LEAD(input, offset, default) - Returns the value of `input` at the `offset`th row after the
* current row in the window. The default value of `offset` is 1 and the default value of `default`
* is null. If the value of `input` at the `offset`th row is null, null is returned. If there is no
* such an offset row (e.g., when the offset is 1, the last row of the window does not have any
* subsequent row), `default` is returned.
*
*
These two aggregate functions are special, and only are used by over window. So here the
* concrete implementation is closely related to {@link OffsetOverFrame}.
*/
public abstract class LeadLagAggFunction extends DeclarativeAggregateFunction {
private int operandCount;
// If the length of function's args is 3, then the function has the default value.
private boolean existDefaultValue;
private UnresolvedReferenceExpression value = unresolvedRef("leadlag");
public LeadLagAggFunction(int operandCount) {
this.operandCount = operandCount;
existDefaultValue = operandCount == 3;
}
@Override
public int operandCount() {
return operandCount;
}
@Override
public UnresolvedReferenceExpression[] aggBufferAttributes() {
return new UnresolvedReferenceExpression[] {value};
}
@Override
public DataType[] getAggBufferTypes() {
return new DataType[] {getResultType()};
}
@Override
public Expression[] initialValuesExpressions() {
return new Expression[] {literal(null, getResultType())};
}
@Override
public Expression[] accumulateExpressions() {
return new Expression[] {operand(0)};
}
// TODO hack, use the current input reset the buffer value.
@Override
public Expression[] retractExpressions() {
return new Expression[] {
existDefaultValue
? cast(operand(2), typeLiteral(getResultType()))
: literal(null, getResultType())
};
}
@Override
public Expression[] mergeExpressions() {
return new Expression[0];
}
@Override
public Expression getValueExpression() {
return value;
}
/** IntLeadLagAggFunction. */
public static class IntLeadLagAggFunction extends LeadLagAggFunction {
public IntLeadLagAggFunction(int operandCount) {
super(operandCount);
}
@Override
public DataType getResultType() {
return DataTypes.INT();
}
}
/** ByteLeadLagAggFunction. */
public static class ByteLeadLagAggFunction extends LeadLagAggFunction {
public ByteLeadLagAggFunction(int operandCount) {
super(operandCount);
}
@Override
public DataType getResultType() {
return DataTypes.TINYINT();
}
}
/** ShortLeadLagAggFunction. */
public static class ShortLeadLagAggFunction extends LeadLagAggFunction {
public ShortLeadLagAggFunction(int operandCount) {
super(operandCount);
}
@Override
public DataType getResultType() {
return DataTypes.SMALLINT();
}
}
/** LongLeadLagAggFunction. */
public static class LongLeadLagAggFunction extends LeadLagAggFunction {
public LongLeadLagAggFunction(int operandCount) {
super(operandCount);
}
@Override
public DataType getResultType() {
return DataTypes.BIGINT();
}
}
/** FloatLeadLagAggFunction. */
public static class FloatLeadLagAggFunction extends LeadLagAggFunction {
public FloatLeadLagAggFunction(int operandCount) {
super(operandCount);
}
@Override
public DataType getResultType() {
return DataTypes.FLOAT();
}
}
/** DoubleLeadLagAggFunction. */
public static class DoubleLeadLagAggFunction extends LeadLagAggFunction {
public DoubleLeadLagAggFunction(int operandCount) {
super(operandCount);
}
@Override
public DataType getResultType() {
return DataTypes.DOUBLE();
}
}
/** BooleanLeadLagAggFunction. */
public static class BooleanLeadLagAggFunction extends LeadLagAggFunction {
public BooleanLeadLagAggFunction(int operandCount) {
super(operandCount);
}
@Override
public DataType getResultType() {
return DataTypes.BOOLEAN();
}
}
/** DecimalLeadLagAggFunction. */
public static class DecimalLeadLagAggFunction extends LeadLagAggFunction {
private final DecimalType decimalType;
public DecimalLeadLagAggFunction(int operandCount, DecimalType decimalType) {
super(operandCount);
this.decimalType = decimalType;
}
@Override
public DataType getResultType() {
return DataTypes.DECIMAL(decimalType.getPrecision(), decimalType.getScale());
}
}
/** StringLeadLagAggFunction. */
public static class StringLeadLagAggFunction extends LeadLagAggFunction {
public StringLeadLagAggFunction(int operandCount) {
super(operandCount);
}
@Override
public DataType getResultType() {
return DataTypes.STRING();
}
}
/** DateLeadLagAggFunction. */
public static class DateLeadLagAggFunction extends LeadLagAggFunction {
public DateLeadLagAggFunction(int operandCount) {
super(operandCount);
}
@Override
public DataType getResultType() {
return DataTypes.DATE();
}
}
/** TimeLeadLagAggFunction. */
public static class TimeLeadLagAggFunction extends LeadLagAggFunction {
public TimeLeadLagAggFunction(int operandCount) {
super(operandCount);
}
@Override
public DataType getResultType() {
return DataTypes.TIME(TimeType.DEFAULT_PRECISION);
}
}
/** TimestampLeadLagAggFunction. */
public static class TimestampLeadLagAggFunction extends LeadLagAggFunction {
private final TimestampType type;
public TimestampLeadLagAggFunction(int operandCount, TimestampType type) {
super(operandCount);
this.type = type;
}
@Override
public DataType getResultType() {
return DataTypes.TIMESTAMP(type.getPrecision());
}
}
}