Factorize pseudo column names and fix comments

Author: fabien.menager

src/PhenX.EntityFrameworkCore.BulkInsert.MySql/MySqlDialectBuilder.cs

@@ -14,15 +14,10 @@ internal class MySqlServerDialectBuilder : SqlDialectBuilder
 
     protected override string CloseDelimiter => "`";
 
-    /// <summary>
-    /// Indicates whether the dialect supports moving rows from temporary table to the final table, in order to
-    /// theoretically reduce disk space requirements.
-    /// </summary>
+    /// <inheritdoc />
     protected override bool SupportsMoveRows => false;
 
-    /// <summary>
-    /// Indicates whether the dialect supports INSERT INTO table AS alias.
-    /// </summary>
+    /// <inheritdoc />
     protected override bool SupportsInsertIntoAlias => false;
 
     public override string CreateTableCopySql(string tempNameName, TableMetadata tableInfo, IReadOnlyList<ColumnMetadata> columns)

src/PhenX.EntityFrameworkCore.BulkInsert.SqlServer/SqlServerDialectBuilder.cs

@@ -71,16 +71,16 @@ public override string BuildMoveDataSql<T>(
                 throw new InvalidOperationException("Table has no primary key that can be used for conflict detection.");
             }
 
-            q.AppendLine($"MERGE INTO {target.QuotedTableName} AS INSERTED");
+            q.AppendLine($"MERGE INTO {target.QuotedTableName} AS {PseudoColumnInserted}");
 
             q.Append("USING (SELECT ");
             q.AppendColumns(insertedColumns);
-            q.Append($" FROM {source}) AS EXCLUDED (");
+            q.Append($" FROM {source}) AS {PseudoColumnExcluded} (");
             q.AppendColumns(insertedColumns);
             q.AppendLine(")");
 
             q.Append("ON ");
-            q.AppendJoin(" AND ", matchColumns, (b, col) => b.Append($"INSERTED.{col} = EXCLUDED.{col}"));
+            q.AppendJoin(" AND ", matchColumns, (b, col) => b.Append($"{PseudoColumnInserted}.{col} = {PseudoColumnExcluded}.{col}"));
             q.AppendLine();
 
             if (onConflictTyped.Update != null)
@@ -110,13 +110,13 @@ public override string BuildMoveDataSql<T>(
             q.AppendLine(")");
 
             q.Append("VALUES (");
-            q.AppendJoin(", ", insertedColumns, (b, col) => b.Append($"EXCLUDED.{col.QuotedColumName}"));
+            q.AppendJoin(", ", insertedColumns, (b, col) => b.Append($"{PseudoColumnExcluded}.{col.QuotedColumName}"));
             q.AppendLine(")");
 
             if (returnedColumns.Count != 0)
             {
                 q.Append("OUTPUT ");
-                q.AppendJoin(", ", returnedColumns, (b, col) => b.Append($"INSERTED.{col.QuotedColumName} AS {col.QuotedColumName}"));
+                q.AppendJoin(", ", returnedColumns, (b, col) => b.Append($"{PseudoColumnInserted}.{col.QuotedColumName} AS {col.QuotedColumName}"));
                 q.AppendLine();
             }
         }
@@ -131,7 +131,7 @@ public override string BuildMoveDataSql<T>(
             if (returnedColumns.Count != 0)
             {
                 q.Append("OUTPUT ");
-                q.AppendJoin(", ", returnedColumns, (b, col) => b.Append($"INSERTED.{col.QuotedColumName} AS {col.QuotedColumName}"));
+                q.AppendJoin(", ", returnedColumns, (b, col) => b.Append($"{PseudoColumnInserted}.{col.QuotedColumName} AS {col.QuotedColumName}"));
                 q.AppendLine();
             }
 

src/PhenX.EntityFrameworkCore.BulkInsert/Dialect/SqlDialectBuilder.cs

@@ -10,11 +10,23 @@ namespace PhenX.EntityFrameworkCore.BulkInsert.Dialect;
 
 internal abstract class SqlDialectBuilder
 {
+    protected const string PseudoColumnInserted = "INSERTED";
+    protected const string PseudoColumnExcluded = "EXCLUDED";
+
     protected abstract string OpenDelimiter { get; }
     protected abstract string CloseDelimiter { get; }
 
     protected virtual string ConcatOperator => "||";
+
+    /// <summary>
+    /// Indicates whether the dialect supports moving rows from temporary table to the final table, in order to
+    /// theoretically reduce disk space requirements.
+    /// </summary>
     protected virtual bool SupportsMoveRows => true;
+
+    /// <summary>
+    /// Indicates whether the dialect supports INSERT INTO table AS alias.
+    /// </summary>
     protected virtual bool SupportsInsertIntoAlias => true;
 
     public abstract string CreateTableCopySql(string tempNameName, TableMetadata tableInfo, IReadOnlyList<ColumnMetadata> columns);
@@ -56,7 +68,7 @@ public virtual string BuildMoveDataSql<T>(
 
         if (SupportsInsertIntoAlias)
         {
-            q.Append(" AS INSERTED");
+            q.Append($" AS {PseudoColumnInserted}");
         }
 
         q.AppendLine(" (");
@@ -156,12 +168,12 @@ protected virtual void AppendConflictCondition<T>(StringBuilder sql, TableMetada
     /// <summary>
     /// Get the name of the INSERTED column (data already in the table) for the ON CONFLICT clause.
     /// </summary>
-    protected virtual string GetInsertedColumnName(string columnName) => $"INSERTED.{Quote(columnName)}";
+    protected virtual string GetInsertedColumnName(string columnName) => $"{PseudoColumnInserted}.{Quote(columnName)}";
 
     /// <summary>
     /// Get the name of the EXCLUDED column (data conflicting with table) for the ON CONFLICT clause.
     /// </summary>
-    protected virtual string GetExcludedColumnName(string columnName) => $"EXCLUDED.{Quote(columnName)}";
+    protected virtual string GetExcludedColumnName(string columnName) => $"{PseudoColumnExcluded}.{Quote(columnName)}";
 
     /// <summary>
     /// Quotes a column name using database-specific delimiters.