JasperFx · jeremydmiller · Jul 18, 2026 · Jul 18, 2026
diff --git a/EFCORE_IMPROVEMENTS.md b/EFCORE_IMPROVEMENTS.md
@@ -128,22 +128,24 @@ Nineteen comparison tests across the permutation matrix:
 
 ## Known gaps (documented, deliberate)
 
-- **Check constraints** are not modeled by Weasel and are invisible to its
-  delta detection; a dedicated test documents the behavior.
-- **Computed columns** (`HasComputedColumnSql`) are not mapped.
-- **Per-column descending sort** and provider index methods (gin/gist) need
-  the `customizeTables` escape hatch.
-- **HiLo / TPC / `HasSequence` sequences** are not managed by Weasel (the
-  columns themselves map correctly as plain columns).
+- **Per-column descending sort** needs the `customizeTables` escape hatch
+  (provider index methods like gin/gist now map automatically via
+  `ITableIndex.Method`).
 - Npgsql `UseIdentityAlwaysColumn` is created as `GENERATED BY DEFAULT`
   (more permissive; inserts behave identically through EF).
 - Alternate keys are created as unique **indexes** rather than unique
   **constraints** — functionally equivalent, including as FK targets, and
   reported as a tolerated difference category by the harness.
-- **Column-default drift is not detected** by delta detection (defaults are
-  applied at creation but `FetchExisting` does not read `column_default`).
-  Reading defaults back would risk spurious migrations for existing Marten
-  schemas, so this remains write-once by design for now.
+- **Column-default drift detection is opt-in** (`ITable.DetectColumnDrift`) —
+  it stays off by default because canonicalizing datetime literals across
+  providers is not stable enough to be safe for existing Marten schemas.
+
+Previously listed gaps now closed: check constraints (modeled with
+conservative delta comparison), computed columns (`HasComputedColumnSql`
+maps to `ITableColumn.ComputedExpression`, is read back by `FetchExisting`
+on PostgreSQL and SQL Server, and participates in delta detection with
+canonicalized expression comparison), and HiLo / `HasSequence` sequences
+(mapped through `Migrator.CreateSequence`).
 
 ## Test infrastructure
 

diff --git a/docs/postgresql/tables.md b/docs/postgresql/tables.md
@@ -44,6 +44,7 @@ The fluent `ColumnExpression` returned by `AddColumn` supports:
 - `DefaultValueByExpression(expr)` -- sets a raw SQL default expression
 - `DefaultValueFromSequence(sequence)` -- uses `nextval()` from a sequence
 - `ForeignKeyTo(table, column)` -- adds an inline foreign key
+- `GeneratedAs(expression)` -- makes this a stored generated column
 
 ## Primary Keys
 
@@ -78,7 +79,7 @@ table.AddColumn<int>("company_id")
     .ForeignKeyTo("companies", "id",
         onDelete: CascadeAction.Cascade);
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/PostgresqlTableSamples.cs#L50-L56' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_pg_foreign_keys' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/PostgresqlTableSamples.cs#L66-L72' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_pg_foreign_keys' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 Or add foreign keys directly to the `ForeignKeys` collection for multi-column keys.
@@ -99,7 +100,7 @@ var index = new IndexDefinition("idx_users_email")
 index.Columns = new[] { "email" };
 table.Indexes.Add(index);
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/PostgresqlTableSamples.cs#L61-L72' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_pg_indexes' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/PostgresqlTableSamples.cs#L77-L88' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_pg_indexes' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 Indexes support GIN, GiST, BRIN, and hash methods via the `IndexMethod` enum. Expression-based indexes and sort order (`SortOrder`, `NullsSortOrder`) are also available.
@@ -117,7 +118,28 @@ table.AddColumn<string>("status").DefaultValueByString("pending");
 table.AddColumn<DateTimeOffset>("created_at")
     .DefaultValueByExpression("now()");
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/PostgresqlTableSamples.cs#L77-L85' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_pg_default_values' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/PostgresqlTableSamples.cs#L93-L101' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_pg_default_values' title='Start of snippet'>anchor</a></sup>
+<!-- endSnippet -->
+
+## Generated Columns
+
+PostgreSQL 12+ supports stored generated columns (`GENERATED ALWAYS AS (...) STORED`). The generation expression is read back from the database catalog by `FetchExisting`, and participates in delta detection with canonicalized expression comparison — changing the expression migrates the column with a lossless drop and re-add (the data is derived). Generated columns the model does not declare are left untouched.
+
+<!-- snippet: sample_pg_generated_columns -->
+<a id='snippet-sample_pg_generated_columns'></a>
+```cs
+var table = new Table("people");
+
+table.AddColumn<string>("first_name");
+table.AddColumn<string>("last_name");
+
+// GENERATED ALWAYS AS (...) STORED — PostgreSQL only supports
+// stored generated columns. The expression is read back from the
+// database catalog and participates in delta detection.
+table.AddColumn("full_name", "text")
+    .GeneratedAs("first_name || ' ' || last_name");
+```
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/PostgresqlTableSamples.cs#L50-L61' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_pg_generated_columns' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 ## Delta Detection and Migration
@@ -143,7 +165,7 @@ var existing = await table.FetchExistingAsync(conn);
 var delta = new TableDelta(table, existing);
 // delta.Difference tells you: None, Create, Update, or Recreate
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/PostgresqlTableSamples.cs#L90-L106' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_pg_table_delta_detection' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/PostgresqlTableSamples.cs#L106-L122' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_pg_table_delta_detection' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 ## Generating DDL
@@ -158,5 +180,5 @@ var writer = new StringWriter();
 table.WriteCreateStatement(migrator, writer);
 Console.WriteLine(writer.ToString());
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/PostgresqlTableSamples.cs#L111-L118' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_pg_table_generate_ddl' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/PostgresqlTableSamples.cs#L127-L134' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_pg_table_generate_ddl' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
diff --git a/docs/sqlserver/functions.md b/docs/sqlserver/functions.md
@@ -18,7 +18,7 @@ RETURN @Price * @Rate;
 END;
 ");
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L201-L210' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_function_from_sql' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L220-L229' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_function_from_sql' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 ## Constructor-Based Creation
@@ -39,7 +39,7 @@ RETURN (SELECT COUNT(*) FROM dbo.users);
 END;
 ");
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L215-L226' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_function_constructor' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L234-L245' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_function_constructor' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 ## Custom Drop Statements
@@ -54,7 +54,7 @@ var fn = new Function(identifier, body, new[]
     "DROP FUNCTION IF EXISTS dbo.GetUserCount;"
 });
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L234-L239' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_function_custom_drop' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L253-L258' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_function_custom_drop' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 ## Delta Detection
@@ -70,7 +70,7 @@ await conn.OpenAsync();
 var delta = await fn.FindDeltaAsync(conn);
 // delta.Difference: None, Create, or Update
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L248-L254' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_function_delta_detection' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L267-L273' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_function_delta_detection' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 ## Marking for Removal
@@ -82,5 +82,5 @@ To generate a drop statement for a function that should be removed:
 ```cs
 var removed = Function.ForRemoval("dbo.ObsoleteFunction");
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L259-L261' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_function_for_removal' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L278-L280' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_function_for_removal' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
diff --git a/docs/sqlserver/procedures.md b/docs/sqlserver/procedures.md
@@ -23,7 +23,7 @@ WHERE Active = 1 AND Age >= @MinAge;
 END;
 ");
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L120-L134' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_define_stored_procedure' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L139-L153' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_define_stored_procedure' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 ## Generating DDL
@@ -43,7 +43,7 @@ proc.WriteCreateOrAlterStatement(migrator, writer);
 // DROP PROCEDURE IF EXISTS
 proc.WriteDropStatement(migrator, writer);
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L142-L154' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_procedure_ddl' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L161-L173' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_procedure_ddl' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 ## Delta Detection
@@ -66,7 +66,7 @@ else if (delta.Difference == SchemaPatchDifference.Update)
     // Procedure body has changed
 }
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L163-L176' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_procedure_delta_detection' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L182-L195' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_procedure_delta_detection' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 ## Fetching Existing Definitions
@@ -80,5 +80,5 @@ if (existing != null)
     // existing contains the current procedure body from the database
 }
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L188-L194' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_procedure_fetch_existing' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L207-L213' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_procedure_fetch_existing' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
diff --git a/docs/sqlserver/sequences.md b/docs/sqlserver/sequences.md
@@ -16,7 +16,7 @@ var seq2 = new Sequence(
     startWith: 1000
 );
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L268-L277' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_define_sequence' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L287-L296' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_define_sequence' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 ## Sequence Ownership
@@ -29,7 +29,7 @@ A sequence can be associated with a table column:
 seq.Owner = DbObjectName.Parse(SqlServerProvider.Instance, "dbo.orders");
 seq.OwnerColumn = "id";
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L284-L287' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_sequence_ownership' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L303-L306' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_sequence_ownership' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 ## Using Sequences with Table Columns
@@ -45,7 +45,7 @@ var seq = new Sequence("dbo.order_seq");
 table.AddColumn<long>("id").AsPrimaryKey()
     .DefaultValueFromSequence(seq);
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L292-L298' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_sequence_with_table' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L311-L317' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_sequence_with_table' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 This generates: `DEFAULT next value for dbo.order_seq`.
@@ -64,7 +64,7 @@ seq.WriteCreateStatement(migrator, writer);
 seq.WriteDropStatement(migrator, writer);
 // Output: DROP SEQUENCE IF EXISTS dbo.order_seq;
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L305-L314' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_sequence_ddl' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L324-L333' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_sequence_ddl' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 ## Delta Detection
@@ -80,5 +80,5 @@ await conn.OpenAsync();
 var delta = await seq.FindDeltaAsync(conn);
 // delta.Difference: None or Create
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L322-L328' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_sequence_delta_detection' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L341-L347' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_sequence_delta_detection' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
diff --git a/docs/sqlserver/table-types.md b/docs/sqlserver/table-types.md
@@ -14,7 +14,7 @@ tableType.AddColumn<int>("product_id").NotNull();
 tableType.AddColumn<int>("quantity").NotNull();
 tableType.AddColumn("unit_price", "decimal(10,2)");
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L335-L342' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_define_table_type' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L354-L361' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_define_table_type' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 ## Column Configuration
@@ -32,7 +32,7 @@ You can add columns by .NET type or by explicit database type string:
 tableType.AddColumn<string>("name");            // maps to varchar(100)
 tableType.AddColumn("notes", "nvarchar(max)");  // explicit type
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L350-L353' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_table_type_columns' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L369-L372' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_table_type_columns' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 ## Generating DDL
@@ -45,7 +45,7 @@ var writer = new StringWriter();
 tableType.WriteCreateStatement(migrator, writer);
 // Output: CREATE TYPE dbo.OrderItemType AS TABLE (product_id int NOT NULL, ...)
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L361-L366' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_table_type_ddl' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L380-L385' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_table_type_ddl' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 ## Delta Detection
@@ -61,7 +61,7 @@ await conn.OpenAsync();
 var delta = await tableType.FindDeltaAsync(conn);
 // delta.Difference: None, Create, or Update
 ```
-<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L375-L381' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_table_type_delta_detection' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/weasel/blob/master/src/DocSamples/SqlServerSamples.cs#L394-L400' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_ss_table_type_delta_detection' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 When an update is needed, the delta generates a DROP followed by CREATE since SQL Server does not support `ALTER TYPE`.