Use server-side zeros trim instead of hinted precision and scale

For expressions as columns we cast to decimal first because there is a chance
it should be done because there is internal cast to decimal and this is the
reason that result type of column is decimal,
For simple column expressions we probably don't need cast, just trim

Author: alex-kulakov

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

@@ -21,6 +21,8 @@ internal class SqlCompiler : Providers.SqlCompiler
   {
     private const int MaxDotnetDecimalPrecision = 28;
 
+    private readonly bool canRemoveInsignificantZerosInDecimal;
+
     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 (canRemoveInsignificantZerosInDecimal) {
+          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)
     {
+      canRemoveInsignificantZerosInDecimal = handlers.ProviderInfo.StorageVersion.Major >= 13;
     }
   }
 }