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hibernate-orm
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fix broken float type precision conversion 

it is not the case that ln(10) = log_2(10)
This commit is contained in:
Gavin King 2021-12-13 09:30:22 +01:00
parent 36be5cc3da
commit 1172943252
3 changed files with 22 additions and 13 deletions
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31
hibernate-core/src/main/java/org/hibernate/dialect/Dialect.java
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@ -161,6 +161,8 @@ import org.hibernate.type.descriptor.jdbc.spi.JdbcTypeRegistry;
import jakarta.persistence.TemporalType;
import static java.lang.Math.ceil;
import static java.lang.Math.log;
import static org.hibernate.type.descriptor.DateTimeUtils.JDBC_ESCAPE_END;
import static org.hibernate.type.descriptor.DateTimeUtils.JDBC_ESCAPE_START_DATE;
import static org.hibernate.type.descriptor.DateTimeUtils.JDBC_ESCAPE_START_TIME;
@ -208,6 +210,9 @@ public abstract class Dialect implements ConversionContext {
private static final Pattern ESCAPE_CLOSING_COMMENT_PATTERN = Pattern.compile( "\\*/" );
private static final Pattern ESCAPE_OPENING_COMMENT_PATTERN = Pattern.compile( "/\\*" );
//needed for converting precision from decimal to binary digits
private static final double LOG_BASE2OF10 = log(10)/log(2);
private final TypeNames typeNames = new TypeNames();
private final TypeNames hibernateTypeNames = new TypeNames();
@ -384,7 +389,7 @@ public abstract class Dialect implements ConversionContext {
return code == Types.FLOAT
&& size != null
&& size.getPrecision() != null
? Size.precision( (int) Math.ceil( size.getPrecision() / 53.0 * 17.0 ) )
? Size.precision( (int) Math.ceil( size.getPrecision() / LOG_BASE2OF10 ) )
: size;
}
@ -3774,20 +3779,24 @@ public abstract class Dialect implements ConversionContext {
case Types.FLOAT:
case Types.DOUBLE:
case Types.REAL:
// The given precision and scale are in decimal numbers as per Javadoc of jakarta.persistence.Column
// but the SQL type FLOAT takes the precision in binary digits,
// so we have to calculate the number of binary digits necessary.
// If the precision and a scale are given, we assume the values are given as decimal digits.
// If just the precision is given, we assume the value is in binary digits already.
if ( precision != null && scale != null ) {
scale = null;
// See https://stackoverflow.com/questions/17415847/how-does-float-map-relate-to-number-in-oracle-10g/17416421
// for the formula which was inverted to calculate the binary digit count
precision = (int) Math.ceil( precision * Math.log( 10 ) );
// this is almost always the thing we use:
size.setPrecision( javaType.getDefaultSqlPrecision( Dialect.this, jdbcType ) );
if (scale != null && scale!=0) {
throw new IllegalArgumentException("scale has no meaning for floating point numbers");
}
// but if the user explicitly specifies a precision, we need to convert it:
if (precision != null) {
// convert from base 10 (as specified in @Column) to base 2 (as specified by SQL)
// using the magic of high school math: log_2(10^n) = n*log_2(10) = n*ln(10)/ln(2)
precision = (int) ceil( precision * LOG_BASE2OF10 );
}
break;
case Types.TIMESTAMP:
case Types.TIMESTAMP_WITH_TIMEZONE:
size.setPrecision( javaType.getDefaultSqlPrecision( Dialect.this, jdbcType ) );
if (scale != null && scale!=0) {
throw new IllegalArgumentException("scale has no meaning for timestamps");
}
break;
case Types.NUMERIC:
case Types.DECIMAL:

2
hibernate-core/src/test/java/org/hibernate/test/annotations/Discount.java
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@ -31,7 +31,7 @@ public class Discount implements Serializable {
private Customer owner;
@Column(precision = 5, scale = 2)
@Column(precision = 5)
public double getDiscount() {
return discount;
}

2
hibernate-envers/src/test/java/org/hibernate/orm/test/envers/integration/onetomany/embeddedid/OneToManyCompositeKeyTest.java
View File

@ -155,7 +155,7 @@ public class OneToManyCompositeKeyTest extends BaseEnversJPAFunctionalTestCase {
@EmbeddedId
private DesignContractId pk = new DesignContractId();
@Basic
@Column(name = "GOAL", nullable = false, precision = 5, scale = 2)
@Column(name = "GOAL", nullable = false, precision = 5)
private Double goal;
DesignContract() {