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more javadoc for Dialect.getFractionalSecondPrecisionInNanos()

This commit is contained in:
Gavin 2023-01-13 23:48:36 +01:00 committed by Gavin King
parent 56774f80d7
commit 8f29ae95c9
4 changed files with 38 additions and 18 deletions
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2
hibernate-community-dialects/src/main/java/org/hibernate/community/dialect/SybaseASELegacyDialect.java
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@ -276,7 +276,6 @@ public class SybaseASELegacyDialect extends SybaseLegacyDialect {
@Override
public String timestampaddPattern(TemporalUnit unit, TemporalType temporalType, IntervalType intervalType) {
//TODO!!
switch ( unit ) {
case NANOSECOND:
return "dateadd(ms,?2/1000000,?3)";
@ -291,7 +290,6 @@ public class SybaseASELegacyDialect extends SybaseLegacyDialect {
@Override
public String timestampdiffPattern(TemporalUnit unit, TemporalType fromTemporalType, TemporalType toTemporalType) {
//TODO!!
switch ( unit ) {
case NANOSECOND:
return "(cast(datediff(ms,?2,?3) as numeric(21))*1000000)";

15
hibernate-core/src/main/java/org/hibernate/dialect/Dialect.java
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@ -4621,7 +4621,22 @@ public abstract class Dialect implements ConversionContext, TypeContributor, Fun
*
* @return the precision, specified as a quantity of
* nanoseconds
*
* @see TemporalUnit#NATIVE
*
* @implNote Getting this right is very important. It
* would be great if all platforms supported
* datetime arithmetic with nanosecond
* precision, since that is how we represent
* {@link Duration}. But they don't, and we
* don't want to fill up the SQL expression
* with many conversions to/from nanoseconds.
* (Not to mention the problems with numeric
* overflow that this sometimes causes.) So
* we need to pick the right value here,
* and implement {@link #timestampaddPattern}
* and {@link #timestampdiffPattern} consistent
* with our choice.
*/
public long getFractionalSecondPrecisionInNanos() {
return 1; //default to nanoseconds for now

25
hibernate-core/src/main/java/org/hibernate/dialect/SQLServerDialect.java
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@ -723,7 +723,7 @@ public class SQLServerDialect extends AbstractTransactSQLDialect {
/**
* SQL server supports up to 7 decimal digits of
* fractional second precision in a datetime2,
* fractional second precision in {@code datetime2},
* but unfortunately its duration arithmetic
* functions have a nasty habit of overflowing.
* So to give ourselves a little extra headroom,
@ -778,16 +778,18 @@ public class SQLServerDialect extends AbstractTransactSQLDialect {
@Override
public String timestampdiffPattern(TemporalUnit unit, TemporalType fromTemporalType, TemporalType toTemporalType) {
if ( unit == TemporalUnit.NATIVE ) {//use microsecond as the "native" precision
if ( unit == TemporalUnit.NATIVE ) {
//use microsecond as the "native" precision
return "datediff_big(microsecond,?2,?3)";
}
//datediff() returns an int, and can easily
//overflow when dealing with "physical"
//durations, so use datediff_big()
return unit.normalized() == NANOSECOND
? "datediff_big(?1,?2,?3)"
: "datediff(?1,?2,?3)";
else {
//datediff() returns an int, and can easily
//overflow when dealing with "physical"
//durations, so use datediff_big()
return unit.normalized() == NANOSECOND
? "datediff_big(?1,?2,?3)"
: "datediff(?1,?2,?3)";
}
}
@Override
@ -796,8 +798,9 @@ public class SQLServerDialect extends AbstractTransactSQLDialect {
if ( unit == TemporalUnit.NATIVE ) {
return "microsecond";
}
return super.translateDurationField( unit );
else {
return super.translateDurationField( unit );
}
}
@Override

14
hibernate-core/src/main/java/org/hibernate/dialect/SybaseASEDialect.java
View File

@ -261,17 +261,22 @@ public class SybaseASEDialect extends SybaseDialect {
return "current_bigdatetime()";
}
/**
* Sybase ASE in principle supports microsecond
* precision for {code bigdatetime}, but
* unfortunately its duration arithmetic
* functions have a nasty habit of overflowing.
* So to give ourselves a little extra headroom,
* we will use {@code millisecond} as the native
* unit of precision.
*/
@Override
public long getFractionalSecondPrecisionInNanos() {
// Sybase supports microsecond precision
// but when we use it we just get numerical
// overflows from timestamp arithmetic
return 1_000_000;
}
@Override
public String timestampaddPattern(TemporalUnit unit, TemporalType temporalType, IntervalType intervalType) {
//TODO!!
switch ( unit ) {
case NANOSECOND:
return "dateadd(ms,?2/1000000,?3)";
@ -286,7 +291,6 @@ public class SybaseASEDialect extends SybaseDialect {
@Override
public String timestampdiffPattern(TemporalUnit unit, TemporalType fromTemporalType, TemporalType toTemporalType) {
//TODO!!
switch ( unit ) {
case NANOSECOND:
return "(cast(datediff(ms,?2,?3) as numeric(21))*1000000)";