Apply 'trim_scale' function to results of aggregation to improve compatibility with .NET decimal

ChangeLog/7.1.6-dev.txt

@@ -0,0 +1 @@
+[postgresql] For PostgreSQL 13+ apply 'trim_scale' function to results of aggregation to improve compatibility with .NET decimal

Orm/Xtensive.Orm.PostgreSql/Orm.Providers.PostgreSql/DomainHandler.cs

@@ -1,4 +1,4 @@
-// Copyright (C) 2008-2020 Xtensive LLC.
+// Copyright (C) 2008-2025 Xtensive LLC.
 // This code is distributed under MIT license terms.
 // See the License.txt file in the project root for more information.
 // Created by: Alexey Gamzov
@@ -18,15 +18,24 @@ namespace Xtensive.Orm.Providers.PostgreSql
   /// </summary>
   public class DomainHandler : Providers.DomainHandler
   {
+    /// <summary>
+    /// <see langword="true"/> if storage can trim insignificant zeros in numeric values
+    /// </summary>
+    protected bool HasNativeTrimOfInsignificantZerosInDecimals =>
+      Handlers.ProviderInfo.StorageVersion.Major >= 13;
+
     /// <inheritdoc/>
     protected override ICompiler CreateCompiler(CompilerConfiguration configuration) =>
       new SqlCompiler(Handlers, configuration);
 
     /// <inheritdoc/>
     protected override IPreCompiler CreatePreCompiler(CompilerConfiguration configuration)
     {
-      var decimalAggregateCorrector = new AggregateOverDecimalColumnCorrector(Handlers.Domain.Model);
-      return new CompositePreCompiler(decimalAggregateCorrector, base.CreatePreCompiler(configuration));
+      if (!HasNativeTrimOfInsignificantZerosInDecimals) {
+        var decimalAggregateCorrector = new AggregateOverDecimalColumnCorrector(Handlers.Domain.Model);
+        return new CompositePreCompiler(decimalAggregateCorrector, base.CreatePreCompiler(configuration));
+      }
+      return base.CreatePreCompiler(configuration);
     }
 
     /// <inheritdoc/>

Orm/Xtensive.Orm.PostgreSql/Orm.Providers.PostgreSql/PostgresqlSqlDml.cs

@@ -1,10 +1,11 @@
-// Copyright (C) 2014-2020 Xtensive LLC.
+// Copyright (C) 2014-2025 Xtensive LLC.
 // This code is distributed under MIT license terms.
 // See the License.txt file in the project root for more information.
 // Created by: Alena Mikshina
 // Created:    2014.05.06;
 
 using Xtensive.Core;
+using Xtensive.Sql;
 using Xtensive.Sql.Dml;
 
 namespace Xtensive.Orm.Providers.PostgreSql
@@ -16,6 +17,15 @@ namespace Xtensive.Orm.Providers.PostgreSql
   /// </summary>
   public class PostgresqlSqlDml
   {
+    /// <summary>
+    /// Creates an expression for native "trim_scale" function call. The function is supported starting from PostgreSQL 13
+    /// </summary>
+    public static SqlExpression DecimalTrimScale(SqlExpression operand)
+    {
+      ArgumentValidator.EnsureArgumentNotNull(operand, nameof(operand));
+      return SqlDml.FunctionCall("TRIM_SCALE", operand);
+    }
+
     #region Spatial types
 
     /// <summary>

Orm/Xtensive.Orm.PostgreSql/Orm.Providers.PostgreSql/SqlCompiler.cs

@@ -1,4 +1,4 @@
-// Copyright (C) 2009-2021 Xtensive LLC.
+// Copyright (C) 2009-2025 Xtensive LLC.
 // This code is distributed under MIT license terms.
 // See the License.txt file in the project root for more information.
 // Created by: Denis Krjuchkov
@@ -21,6 +21,8 @@ internal class SqlCompiler : Providers.SqlCompiler
   {
     private const int MaxDotnetDecimalPrecision = 28;
 
+    private readonly bool canRemoveInsignificantZerosInDecimals;
+
     protected override SqlProvider VisitFreeText(FreeTextProvider provider)
     {
       var rankColumnName = provider.Header.Columns[provider.Header.Columns.Count - 1].Name;
@@ -61,6 +63,11 @@ protected override SqlExpression ProcessAggregate(SqlProvider source, List<SqlEx
       var aggregateType = aggregateColumn.AggregateType;
       var originCalculateColumn = source.Origin.Header.Columns[aggregateColumn.SourceIndex];
       if (AggregateRequiresDecimalAdjustments(aggregateColumn)) {
+        if (canRemoveInsignificantZerosInDecimals) {
+          return (IsCalculatedColumn(originCalculateColumn))
+            ? PostgresqlSqlDml.DecimalTrimScale(SqlDml.Cast(result, Driver.MapValueType(aggregateColumn.Type)))
+            : PostgresqlSqlDml.DecimalTrimScale(result);
+        }
         if (!IsCalculatedColumn(originCalculateColumn)) {
           // this is aggregate by one column, result will be defined by the precision and scale of the column
           return result;
@@ -138,6 +145,7 @@ AggregateType.Min or
     public SqlCompiler(HandlerAccessor handlers, CompilerConfiguration configuration)
       : base(handlers, configuration)
     {
+      canRemoveInsignificantZerosInDecimals = handlers.ProviderInfo.StorageVersion.Major >= 13;
     }
   }
 }