Merge 'translate/upsert: use emit_column_or_rowid for DO UPDATE row snapshot' from ongyimeng

- In core/translate/upsert.rs, conflicting-row snapshots now use
emit_column_or_rowid(...)
- Replaces manual Column { default: None } handling
- Adds regression test in testing/sqltests/tests/upsert.sqltest
- UPSERT was reading NULL in cases where SQLite expects the column’s
default value
- This happens for missing trailing column values after ALTER TABLE ...
ADD COLUMN ... DEFAULT ...
- The fix restores SQLite-compatible behavior
- Applies specifically to the DO UPDATE path of UPSERT
Issue #6087
Used AI to trace the issue to upsert.rs, propose the minimal fix, and
draft the regression test.

Closes #6118

Author: PThorpe92

core/translate/upsert.rs

@@ -411,25 +411,16 @@ pub fn emit_upsert(
     let layout = ctx.table.column_layout();
 
     let current_start = program.alloc_registers(num_cols);
-    for (i, col) in ctx.table.columns.iter().enumerate() {
+    for i in 0..num_cols {
+        let col = &table.columns()[i];
         let reg = layout.to_register(current_start, i);
         if col.is_virtual_generated() {
             program.emit_insn(Insn::Null {
                 dest: reg,
                 dest_end: None,
             });
-        } else if col.is_rowid_alias() {
-            program.emit_insn(Insn::RowId {
-                cursor_id: ctx.cursor_id,
-                dest: reg,
-            });
         } else {
-            program.emit_insn(Insn::Column {
-                cursor_id: ctx.cursor_id,
-                column: layout.to_reg_offset(i),
-                dest: reg,
-                default: None,
-            });
+            program.emit_column_or_rowid(ctx.cursor_id, i, reg);
         }
     }
 

testing/sqltests/tests/snapshot_tests/returning/snapshots/returning__upsert-returning.snap

@@ -47,7 +47,7 @@ addr  opcode         p1  p2  p3  p4   p5  comment
   28  SeekRowid       1   1  49        0  if (r[1]!=cursor 1 for table t2.rowid) goto 49
   29  RowId           1  15   0        0  r[15]=t2.rowid
   30  Column          1   1  16        0  r[16]=t2.name
-  31  Column          1   2  17        0  r[17]=t2.counter
+  31  Column          1   2  17  0     0  r[17]=t2.counter
   32  Copy           15  18   2        0  r[18]=r[15]
   33  Copy           17  21   0        0  r[21]=r[17]
   34  Integer         1  22   0        0  r[22]=1

testing/sqltests/tests/upsert.sqltest

@@ -81,6 +81,20 @@ expect {
     1|11|new
 }
 
+@cross-check-integrity
+test upsert-do-update-reads-added-column-default-for-prealter-row {
+    CREATE TABLE t(id INTEGER PRIMARY KEY, name TEXT);
+    INSERT INTO t VALUES(1, 'alice');
+    ALTER TABLE t ADD COLUMN score INTEGER DEFAULT 42;
+
+    INSERT INTO t VALUES(1, 'bob', 0)
+      ON CONFLICT(id) DO UPDATE SET score = score + 1;
+    SELECT * FROM t;
+}
+expect {
+    1|alice|43
+}
+
 @cross-check-integrity
 test upsert-values-mixed-insert-update {
     CREATE TABLE m (a UNIQUE, b);