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new 4c6df9062e [fix](DECIMALV3)fix cumulative precision when literal and
DECIMALV3 operations in Legacy (#20354)
4c6df9062e is described below
commit 4c6df9062ecf39acb80469fc586e1e75e53ac010
Author: Mryange <59914473+mrya...@users.noreply.github.com>
AuthorDate: Fri Jun 9 08:58:55 2023 +0800
[fix](DECIMALV3)fix cumulative precision when literal and DECIMALV3
operations in Legacy (#20354)
The precision handling for division with DECIMALV3 is as follows (excluding
cases where division increases precision):
(p1, s1) / (p2, s2) ----> (p1 + s2, s1)
However, due to precision loss in division, it is considered to increase
the precision of the left operand:
(p1, s1) / (p2, s2) =====> (p1 + s2, s1 + s2) / (p2, s2) ----> (p1 + s2, s1)
However, the legacy optimizer repeats the analyze and substitute steps for
an expression, which can result in the accumulation of precision:
(p1, s1) / (p2, s2) =====> (p1 + s2, s1 + s2) / (p2, s2) =====> (p1 + s2 +
s2, s1 + s2 + s2) / (p2, s2)
To address this, the previous approach was to forcibly convert the left
operand of DECIMALV3 calculations. This results in rewriting the expression as:
(p1, s1) / (p2, s2) =====> cast((p1, s1) as (p1 + s2, s1 + s2)) / (p2, s2)
Then, during the substitution step, a check is performed. If it is a cast
expression, the expression modified by the cast is extracted:
cast((p1, s1) as (p1 + s2, s1 + s2)) =====> (p1, s1)
protected Expr substituteImpl(ExprSubstitutionMap smap, ExprSubstitutionMap
disjunctsMap, Analyzer analyzer) {
if (isImplicitCast()) {
return getChild(0).substituteImpl(smap, disjunctsMap, analyzer);
}
This way, there won't be repeated analysis, preventing the continuous
increase in precision. However, if the left expression is a constant (literal),
theoretically, the precision would continue to increase. Unfortunately, the
code that was removed in this PR (#19926) obscured this issue.
for (Expr child : children) {
if (child instanceof DecimalLiteral && child.getType().isDecimalV3()) {
((DecimalLiteral)child).tryToReduceType();
}
}
An attempt will be made to reduce the precision of literals in the
expressions. However, this code snippet can cause such a bug.
mysql [test]>select cast(1 as DECIMALV3(16, 2)) / cast(3 as DECIMALV3(16,
2));
+-----------------------------------------------------------+
| CAST(1 AS DECIMALV3(16, 2)) / CAST(3 AS DECIMALV3(16, 2)) |
+-----------------------------------------------------------+
| 0.00 |
+-----------------------------------------------------------+
1.00 / 3.00, due to reduced precision, becomes 1 / 3.
<--Describe your changes.-->
---
.../main/java/org/apache/doris/analysis/ArithmeticExpr.java | 12 ++++++++++--
.../src/main/java/org/apache/doris/analysis/CastExpr.java | 10 ++++++++++
.../main/java/org/apache/doris/analysis/DecimalLiteral.java | 7 +++++++
.../java/org/apache/doris/rewrite/FoldConstantsRule.java | 3 +++
regression-test/data/correctness/test_cast_as_decimalv3.out | 11 ++++++++---
.../suites/correctness/test_cast_as_decimalv3.groovy | 3 +++
6 files changed, 41 insertions(+), 5 deletions(-)
diff --git
a/fe/fe-core/src/main/java/org/apache/doris/analysis/ArithmeticExpr.java
b/fe/fe-core/src/main/java/org/apache/doris/analysis/ArithmeticExpr.java
index 3df32f0ae9..1a962680e2 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/analysis/ArithmeticExpr.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/analysis/ArithmeticExpr.java
@@ -505,7 +505,7 @@ public class ArithmeticExpr extends Expr {
if (((ScalarType) type).getScalarScale() != ((ScalarType)
children.get(1).type).getScalarScale()) {
castChild(type, 1);
}
- } else if (op == Operator.DIVIDE &&
t1TargetType.isDecimalV3()) {
+ } else if (op == Operator.DIVIDE &&
(t1TargetType.isDecimalV3())) {
int leftPrecision = t1Precision + t2Scale +
Config.div_precision_increment;
int leftScale = t1Scale + t2Scale +
Config.div_precision_increment;
if (leftPrecision > ScalarType.MAX_DECIMAL128_PRECISION) {
@@ -515,7 +515,15 @@ public class ArithmeticExpr extends Expr {
type = castBinaryOp(Type.DOUBLE);
break;
}
- castChild(ScalarType.createDecimalV3Type(leftPrecision,
leftScale), 0);
+ Expr child = getChild(0);
+ if (child instanceof DecimalLiteral) {
+ DecimalLiteral literalChild = (DecimalLiteral) child;
+ Expr newChild = literalChild
+
.castToDecimalV3ByDivde(ScalarType.createDecimalV3Type(leftPrecision,
leftScale));
+ setChild(0, newChild);
+ } else {
+
castChild(ScalarType.createDecimalV3Type(leftPrecision, leftScale), 0);
+ }
} else if (op == Operator.MOD) {
// TODO use max int part + max scale of two operands as
result type
// because BE require the result and operands types are
the exact the same decimalv3 type
diff --git a/fe/fe-core/src/main/java/org/apache/doris/analysis/CastExpr.java
b/fe/fe-core/src/main/java/org/apache/doris/analysis/CastExpr.java
index 8cc25b9b27..be93975efb 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/analysis/CastExpr.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/analysis/CastExpr.java
@@ -63,6 +63,8 @@ public class CastExpr extends Expr {
// True if this cast does not change the type.
private boolean noOp = false;
+ private boolean notFold = false;
+
private static final Map<Pair<Type, Type>, Function.NullableMode>
TYPE_NULLABLE_MODE;
static {
@@ -582,5 +584,13 @@ public class CastExpr extends Expr {
public String getStringValueForArray() {
return children.get(0).getStringValueForArray();
}
+
+ public void setNotFold(boolean notFold) {
+ this.notFold = notFold;
+ }
+
+ public boolean isNotFold() {
+ return this.notFold;
+ }
}
diff --git
a/fe/fe-core/src/main/java/org/apache/doris/analysis/DecimalLiteral.java
b/fe/fe-core/src/main/java/org/apache/doris/analysis/DecimalLiteral.java
index 81fe2bf755..47e98e1142 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/analysis/DecimalLiteral.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/analysis/DecimalLiteral.java
@@ -384,6 +384,13 @@ public class DecimalLiteral extends LiteralExpr {
return super.uncheckedCastTo(targetType);
}
+ public Expr castToDecimalV3ByDivde(Type targetType) {
+ // onlye use in DecimalLiteral divide DecimalV3
+ CastExpr expr = new CastExpr(targetType, this);
+ expr.setNotFold(true);
+ return expr;
+ }
+
@Override
public int hashCode() {
return 31 * super.hashCode() + Objects.hashCode(value);
diff --git
a/fe/fe-core/src/main/java/org/apache/doris/rewrite/FoldConstantsRule.java
b/fe/fe-core/src/main/java/org/apache/doris/rewrite/FoldConstantsRule.java
index dcc0bede70..8b65597812 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/rewrite/FoldConstantsRule.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/rewrite/FoldConstantsRule.java
@@ -109,6 +109,9 @@ public class FoldConstantsRule implements ExprRewriteRule {
// cast-to-types and that can lead to query failures, e.g., CTAS
if (expr instanceof CastExpr) {
CastExpr castExpr = (CastExpr) expr;
+ if (castExpr.isNotFold()) {
+ return castExpr;
+ }
if (castExpr.getChild(0) instanceof NullLiteral) {
return castExpr.getChild(0);
}
diff --git a/regression-test/data/correctness/test_cast_as_decimalv3.out
b/regression-test/data/correctness/test_cast_as_decimalv3.out
index 2e7ab315b3..9032acc1ee 100644
--- a/regression-test/data/correctness/test_cast_as_decimalv3.out
+++ b/regression-test/data/correctness/test_cast_as_decimalv3.out
@@ -1,9 +1,14 @@
-- This file is automatically generated. You should know what you did if you
want to edit this
-- !select1 --
-0.333333333333333333333333
-0.250000000000000000000000
-0.200000000000000000000000
+0.333333
+0.250000
+0.200000
-- !select2 --
0.333333
+-- !select3 --
+0.33333
+0.25000
+0.20000
+
diff --git a/regression-test/suites/correctness/test_cast_as_decimalv3.groovy
b/regression-test/suites/correctness/test_cast_as_decimalv3.groovy
index 6bf346ad87..b7e4998a23 100644
--- a/regression-test/suites/correctness/test_cast_as_decimalv3.groovy
+++ b/regression-test/suites/correctness/test_cast_as_decimalv3.groovy
@@ -47,4 +47,7 @@ suite("test_cast_as_decimalv3") {
qt_select2 """
select cast(1 as DECIMALV3(5, 2)) / cast(3 as DECIMALV3(5, 2))
"""
+ qt_select3 """
+ select 1.0 / val from divtest order by id
+ """
}
\ No newline at end of file
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