Sync Repos: Release 170.191 (#193)

* Fix allocation performance issue in ScriptWriter token list initialization

* Add SQL Server 2025 TOP WITH APPROXIMATE and FETCH APPROXIMATE support

* Adding release notes for 170.191.0

Author: ssreerama

SqlScriptDom/Parser/TSql/Ast.xml

@@ -3630,10 +3630,12 @@
     <Member Name="Expression" Type="ScalarExpression" Summary="The expression."/>
     <Member Name="Percent" Type="bool" Summary="True if PERCENT keyword was used."/>
     <Member Name="WithTies" Type="bool" Summary="True is WITH TIES keywords were used. Important: The interpreter has to check there is an order by clause."/>
+    <Member Name="WithApproximate" Type="bool" Summary="True if WITH APPROXIMATE (or APPROX) keyword was used. Introduced in SQL Server 2025 for approximate query processing."/>
   </Class>
   <Class Name="OffsetClause" Summary="This class represents an offset/fetch filter, that can be used in select statements for paging the result set.">
     <Member Name="OffsetExpression" Type="ScalarExpression" Summary="Expression for number fo rows to skip."/>
     <Member Name="FetchExpression" Type="ScalarExpression" Summary="Expression for number fo rows to return."/>
+    <Member Name="WithApproximate" Type="bool" Summary="True if FETCH APPROXIMATE (or APPROX) keyword was used. Only valid in SQL Server 2025 (170) and above. Note: APPROXIMATE is not valid with OFFSET; only FETCH APPROXIMATE is supported."/>
   </Class>
   <Class Name="UnaryExpression" Base="ScalarExpression" Summary="An expression that has a single expression as child.">
     <Member Name="UnaryExpressionType" Type="UnaryExpressionType" GenerateUpdatePositionInfoCall="false" Summary="The type of the expression."/>

SqlScriptDom/Parser/TSql/CodeGenerationSupporter.cs

@@ -143,6 +143,8 @@ internal static class CodeGenerationSupporter
         internal const string Atomic = "ATOMIC";
         internal const string Append = "APPEND";
         internal const string AppendOnly = "APPEND_ONLY";
+        internal const string Approximate = "APPROXIMATE";
+        internal const string Approx = "APPROX";
         internal const string Avg = "AVG";
         internal const string Attested = "ATTESTED";
         internal const string AuditGuid = "AUDIT_GUID";

SqlScriptDom/Parser/TSql/TSql170.g

@@ -18389,33 +18389,99 @@ offsetClause returns [OffsetClause vResult = this.FragmentFactory.CreateFragment
     ScalarExpression vExpression;
 }
     :
-        tOffset:Identifier vExpression = expression
-        {
-            Match(tOffset, CodeGenerationSupporter.Offset);
-            UpdateTokenInfo(vResult,tOffset);
-            vResult.OffsetExpression = vExpression;
-        }
-        tOffsetRowOrRows:Identifier
-        {
-            Match(tOffsetRowOrRows, CodeGenerationSupporter.Row, CodeGenerationSupporter.Rows);
-            UpdateTokenInfo(vResult,tOffsetRowOrRows);
-        }
         (
-            options {greedy=true;} : //Greedy due to conflict with FETCH statements
-            tFetch:Fetch tFirstOrNext:Identifier vExpression = expression
+            // Pattern 1: OFFSET with optional FETCH
+            tOffset:Identifier vExpression = expression
+            {
+                Match(tOffset, CodeGenerationSupporter.Offset);
+                UpdateTokenInfo(vResult,tOffset);
+                vResult.OffsetExpression = vExpression;
+            }
+            tOffsetRowOrRows:Identifier
+            {
+                Match(tOffsetRowOrRows, CodeGenerationSupporter.Row, CodeGenerationSupporter.Rows);
+                UpdateTokenInfo(vResult,tOffsetRowOrRows);
+            }
+            (
+                options {greedy=true;} : //Greedy due to conflict with FETCH statements
+                tFetch:Fetch
+                tFirstOrNext:Identifier
+                {
+                    // Check if this is APPROXIMATE/APPROX before FIRST/NEXT
+                    if (TryMatch(tFirstOrNext, CodeGenerationSupporter.Approximate) ||
+                        TryMatch(tFirstOrNext, CodeGenerationSupporter.Approx))
+                    {
+                        vResult.WithApproximate = true;
+                        UpdateTokenInfo(vResult,tFirstOrNext);
+                        
+                        // Consume the actual FIRST/NEXT token
+                        tFirstOrNext = LT(1);
+                        consume();
+                        Match(tFirstOrNext, CodeGenerationSupporter.First, CodeGenerationSupporter.Next);
+                        UpdateTokenInfo(vResult,tFirstOrNext);
+                    }
+                    else
+                    {
+                        // This is the FIRST/NEXT token directly
+                        Match(tFirstOrNext, CodeGenerationSupporter.First, CodeGenerationSupporter.Next);
+                        UpdateTokenInfo(vResult,tFirstOrNext);
+                    }
+                }
+                vExpression = expression
+                {
+                    vResult.FetchExpression = vExpression;
+                }
+                tFetchRowOrRows:Identifier tOnly:Identifier
+                {
+                    Match(tFetchRowOrRows, CodeGenerationSupporter.Row, CodeGenerationSupporter.Rows);
+                    Match(tOnly, CodeGenerationSupporter.Only);
+                    UpdateTokenInfo(vResult, tOnly);
+                    
+                    // Validate: OFFSET cannot be used with FETCH APPROXIMATE
+                    ValidateFetchApproximate(vResult);
+                }
+            )?
+        |
+            // Pattern 2: Standalone FETCH (APPROXIMATE only in TSql170+)
+            tFetch2:Fetch
+            {
+                UpdateTokenInfo(vResult,tFetch2);
+            }
+            tFirstOrNext2:Identifier
+            {
+                // Check if this is APPROXIMATE/APPROX before FIRST/NEXT
+                if (TryMatch(tFirstOrNext2, CodeGenerationSupporter.Approximate) ||
+                    TryMatch(tFirstOrNext2, CodeGenerationSupporter.Approx))
+                {
+                    vResult.WithApproximate = true;
+                    UpdateTokenInfo(vResult,tFirstOrNext2);
+                    
+                    // Consume the actual FIRST/NEXT token
+                    tFirstOrNext2 = LT(1);
+                    consume();
+                    Match(tFirstOrNext2, CodeGenerationSupporter.First, CodeGenerationSupporter.Next);
+                    UpdateTokenInfo(vResult,tFirstOrNext2);
+                }
+                else
+                {
+                    // This is the FIRST/NEXT token directly
+                    Match(tFirstOrNext2, CodeGenerationSupporter.First, CodeGenerationSupporter.Next);
+                    UpdateTokenInfo(vResult,tFirstOrNext2);
+                }
+            }
+            vExpression = expression
             {
-                UpdateTokenInfo(vResult,tFetch);
-                Match(tFirstOrNext, CodeGenerationSupporter.First, CodeGenerationSupporter.Next);
-                UpdateTokenInfo(vResult,tFirstOrNext);
                 vResult.FetchExpression = vExpression;
             }
-            tFetchRowOrRows:Identifier tOnly:Identifier
+            tFetchRowOrRows2:Identifier tOnly2:Identifier
             {
-                Match(tFetchRowOrRows, CodeGenerationSupporter.Row, CodeGenerationSupporter.Rows);
-                Match(tOnly, CodeGenerationSupporter.Only);
-                UpdateTokenInfo(vResult, tOnly);
+                Match(tFetchRowOrRows2, CodeGenerationSupporter.Row, CodeGenerationSupporter.Rows);
+                Match(tOnly2, CodeGenerationSupporter.Only);
+                UpdateTokenInfo(vResult, tOnly2);
+                
+                // No validation needed for standalone FETCH APPROXIMATE (no OFFSET present)
             }
-        )?
+        )
     ;
 
 // This rule corresponds to topn in Sql Server grammar.
@@ -18447,9 +18513,18 @@ topRowFilter returns [TopRowFilter vResult = this.FragmentFactory.CreateFragment
         (
             With tId:Identifier
             {
-                Match(tId,CodeGenerationSupporter.Ties);
-                UpdateTokenInfo(vResult,tId);
-                vResult.WithTies = true;
+                if (TryMatch(tId, CodeGenerationSupporter.Approximate) ||
+                    TryMatch(tId, CodeGenerationSupporter.Approx))
+                {
+                    UpdateTokenInfo(vResult,tId);
+                    vResult.WithApproximate = true;
+                }
+                else
+                {
+                    Match(tId,CodeGenerationSupporter.Ties);
+                    UpdateTokenInfo(vResult,tId);
+                    vResult.WithTies = true;
+                }
             }
         )?
     ;

SqlScriptDom/Parser/TSql/TSql170ParserBaseInternal.cs

@@ -109,5 +109,21 @@ protected bool ContainsVectorInLookahead()
 
             return false;
         }
+
+        /// <summary>
+        /// Validates that OFFSET is not used with FETCH APPROXIMATE.
+        /// SQL Server does not support combining OFFSET with FETCH APPROXIMATE.
+        /// </summary>
+        /// <param name="offsetClause">The offset clause to validate.</param>
+        protected void ValidateFetchApproximate(OffsetClause offsetClause)
+        {
+            if (offsetClause != null && 
+                offsetClause.WithApproximate && 
+                offsetClause.OffsetExpression != null)
+            {
+                ThrowParseErrorException("SQL46145", offsetClause, 
+                    TSqlParserResource.SQL46145Message);
+            }
+        }
     }
 }

SqlScriptDom/ScriptDom/SqlServer/ScriptGenerator/ScriptWriter.cs

@@ -321,7 +321,7 @@ private List<TSqlParserToken> Align()
             }
 
             // generate aligned token stream
-            List<TSqlParserToken> tokens = new List<TSqlParserToken>();
+            List<TSqlParserToken> tokens = new List<TSqlParserToken>(_scriptWriterElements.Count);
 
             Int32 offset = 0;
             for (Int32 index = 0; index < _scriptWriterElements.Count; ++index)

SqlScriptDom/ScriptDom/SqlServer/ScriptGenerator/SqlScriptGeneratorVisitor.OffsetClause.cs

@@ -14,13 +14,27 @@ public override void ExplicitVisit(OffsetClause node)
             AlignmentPoint start = new AlignmentPoint();
             MarkAndPushAlignmentPoint(start);
 
-            GenerateIdentifier(CodeGenerationSupporter.Offset);
-            GenerateSpaceAndFragmentIfNotNull(node.OffsetExpression);
-            GenerateSpaceAndIdentifier(CodeGenerationSupporter.Rows);
+            if (node.OffsetExpression != null)
+            {
+                GenerateIdentifier(CodeGenerationSupporter.Offset);
+                GenerateSpaceAndFragmentIfNotNull(node.OffsetExpression);
+                GenerateSpaceAndIdentifier(CodeGenerationSupporter.Rows);
+            }
 
             if (node.FetchExpression != null)
             {
-                GenerateSpaceAndKeyword(TSqlTokenType.Fetch);
+                if (node.OffsetExpression != null)
+                {
+                    GenerateSpace();
+                }
+                
+                GenerateKeyword(TSqlTokenType.Fetch);
+                
+                if (node.WithApproximate)
+                {
+                    GenerateSpaceAndIdentifier(CodeGenerationSupporter.Approximate);
+                }
+                
                 GenerateSpaceAndIdentifier(CodeGenerationSupporter.Next);
                 GenerateSpaceAndFragmentIfNotNull(node.FetchExpression);
                 GenerateSpaceAndIdentifier(CodeGenerationSupporter.Rows);

SqlScriptDom/ScriptDom/SqlServer/ScriptGenerator/SqlScriptGeneratorVisitor.TopRowFilter.cs

@@ -19,10 +19,19 @@ public override void ExplicitVisit(TopRowFilter node)
                 GenerateSpaceAndKeyword(TSqlTokenType.Percent); 
             }
 
-            if (node.WithTies)
+            if (node.WithTies || node.WithApproximate)
             {
                 GenerateSpaceAndKeyword(TSqlTokenType.With);
-                GenerateSpaceAndIdentifier(CodeGenerationSupporter.Ties); 
+                
+                if (node.WithApproximate)
+                {
+                    GenerateSpaceAndIdentifier(CodeGenerationSupporter.Approximate);
+                }
+                
+                if (node.WithTies)
+                {
+                    GenerateSpaceAndIdentifier(CodeGenerationSupporter.Ties); 
+                }
             }
         }
     }

SqlScriptDom/TSqlParserResource.Designer.cs

@@ -631,4 +631,7 @@
   <data name="SQL46144Message" xml:space="preserve">
     <value>Required parameter {0} must be provided.</value>
   </data>
+  <data name="SQL46145Message" xml:space="preserve">
+    <value>OFFSET clause cannot be used with FETCH APPROXIMATE. Use FETCH APPROXIMATE without OFFSET.</value>
+  </data>
 </root>

SqlScriptDom/TSqlParserResource.resx

@@ -0,0 +1,34 @@
+SELECT OrderID,
+       CustomerName
+FROM Orders
+ORDER BY OrderDate
+FETCH APPROXIMATE NEXT 20 ROWS ONLY;
+
+SELECT OrderID,
+       CustomerName
+FROM Orders
+ORDER BY OrderDate
+FETCH APPROXIMATE NEXT 20 ROWS ONLY;
+
+SELECT ProductID,
+       ProductName
+FROM Products
+ORDER BY Price
+FETCH APPROXIMATE NEXT 15 ROWS ONLY;
+
+DECLARE @take AS INT = 50;
+
+SELECT OrderID,
+       CustomerName,
+       OrderDate
+FROM Orders
+ORDER BY OrderDate
+FETCH APPROXIMATE NEXT @take ROWS ONLY;
+
+SELECT TOP 100 *
+FROM (SELECT OrderID,
+             CustomerName
+      FROM Orders
+      ORDER BY OrderDate
+      FETCH APPROXIMATE NEXT 1000 ROWS ONLY) AS RecentOrders
+ORDER BY OrderID;