Adds setting ForceListExpansion to provide a way to enable consiste…

…nt handling of list parameters regardless of RDBMS (DapperLib#1871)

Dapper/SqlMapper.Settings.cs

@@ -99,6 +99,13 @@ public static void SetDefaults()
             /// instead of the original name; for most scenarios, this is ignored since the name is redundant, but "snowflake" requires this.
             /// </summary>
             public static bool UseIncrementalPseudoPositionalParameterNames { get; set; }
+
+            /// <summary>
+            /// If set, this causes Dapper to perform list expansion on all lists provided as query parameters, regardless of whether the underlying
+            /// database has native support for lists or not. Enabling this makes it possible to write queries expecting list parameters that work
+            /// on databases that support lists, as well as database that do not. See https://github.com/DapperLib/Dapper/issues/1871.
+            /// </summary>
+            public static bool ForceListExpansion { get; set; }
         }
     }
 }

Dapper/SqlMapper.cs

@@ -2022,7 +2022,7 @@ public static void PackListParameters(IDbCommand command, string namePrefix, obj
             // initially we tried TVP, however it performs quite poorly.
             // keep in mind SQL support up to 2000 params easily in sp_executesql, needing more is rare
 
-            if (FeatureSupport.Get(command.Connection).Arrays)
+            if (FeatureSupport.Get(command.Connection).Arrays && !Settings.ForceListExpansion)
             {
                 var arrayParm = command.CreateParameter();
                 arrayParm.Value = SanitizeParameterValue(value);

Readme.md

@@ -230,7 +230,7 @@ When an object that implements the `IDynamicParameters` interface passed into `E
 
 List Support
 ------------
-Dapper allows you to pass in `IEnumerable<int>` and will automatically parameterize your query.
+Dapper allows you to pass in `IEnumerable<int>` and will automatically parameterize your query, if your database driver does not natively have support for passing a list as a parameter.
 
 For example:
 
@@ -244,6 +244,13 @@ Will be translated to:
 select * from (select 1 as Id union all select 2 union all select 3) as X where Id in (@Ids1, @Ids2, @Ids3)" // @Ids1 = 1 , @Ids2 = 2 , @Ids2 = 3
 ```
 
+For database drivers that do support list parameters (at this time, Postgres and ClickHouse), list expansion is not performed, as it is not required. However, automatic expansion can be enabled by setting a global flag, if the need arises, such as in writing SQL that is used by multiple databases, where only some of the target databases support lists natively.
+
+```csharp
+// This setting is false, by default.
+SqlMapper.Settings.ForceListExpansion = true;
+```
+
 Literal replacements
 ------------
 Dapper supports literal replacements for bool and numeric types.