From 2ca99ced539134d7613bb9b48ac6a817d2b6e5c0 Mon Sep 17 00:00:00 2001
From: Jack Christensen <jack@jackchristensen.com>
Date: Sat, 25 May 2024 09:00:44 -0500
Subject: [PATCH 1/2] database/sql: Add RowsColumnScanner interface

Implementing RowsColumnScanner allows the driver
to completely control how values are scanned.

Fixes #67546
---
 src/database/sql/driver/driver.go | 10 ++++++++++
 src/database/sql/sql.go           | 11 ++++++++++-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/database/sql/driver/driver.go b/src/database/sql/driver/driver.go
index da310bfb12a0b..f70cdcb44e12d 100644
--- a/src/database/sql/driver/driver.go
+++ b/src/database/sql/driver/driver.go
@@ -515,6 +515,16 @@ type RowsColumnTypePrecisionScale interface {
 	ColumnTypePrecisionScale(index int) (precision, scale int64, ok bool)
 }
 
+// RowsColumnScanner may be implemented by [Rows]. It allows the driver to control
+// how values or scanned.
+type RowsColumnScanner interface {
+	Rows
+
+	// ScanColumn copies the column in the current row into the value pointed at by
+	// dest. It returns [ErrSkip] to fall back to the normal [database/sql] scanning path.
+	ScanColumn(index int, dest any) error
+}
+
 // Tx is a transaction.
 type Tx interface {
 	Commit() error
diff --git a/src/database/sql/sql.go b/src/database/sql/sql.go
index de774a051093d..8d15e065b9136 100644
--- a/src/database/sql/sql.go
+++ b/src/database/sql/sql.go
@@ -3389,7 +3389,16 @@ func (rs *Rows) Scan(dest ...any) error {
 	}
 
 	for i, sv := range rs.lastcols {
-		err := convertAssignRows(dest[i], sv, rs)
+		err := driver.ErrSkip
+
+		if rowsColumnScanner, ok := rs.rowsi.(driver.RowsColumnScanner); ok {
+			err = rowsColumnScanner.ScanColumn(i, dest[i])
+		}
+
+		if err == driver.ErrSkip {
+			err = convertAssignRows(dest[i], sv, rs)
+		}
+
 		if err != nil {
 			rs.closemuRUnlockIfHeldByScan()
 			return fmt.Errorf(`sql: Scan error on column index %d, name %q: %w`, i, rs.rowsi.Columns()[i], err)

From 45049970986abeb66b059d548336dad70c1b0023 Mon Sep 17 00:00:00 2001
From: Jack Christensen <jack@jackchristensen.com>
Date: Mon, 24 Jun 2024 20:17:09 -0500
Subject: [PATCH 2/2] Expand RowsColumnScanner documentation

---
 src/database/sql/driver/driver.go | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/database/sql/driver/driver.go b/src/database/sql/driver/driver.go
index f70cdcb44e12d..d3fa1f6778eff 100644
--- a/src/database/sql/driver/driver.go
+++ b/src/database/sql/driver/driver.go
@@ -515,8 +515,10 @@ type RowsColumnTypePrecisionScale interface {
 	ColumnTypePrecisionScale(index int) (precision, scale int64, ok bool)
 }
 
-// RowsColumnScanner may be implemented by [Rows]. It allows the driver to control
-// how values or scanned.
+// RowsColumnScanner may be implemented by [Rows]. It allows the driver to completely
+// take responsibility for how values are scanned and replace the normal [database/sql].
+// scanning path. This allows drivers to directly support types that do not implement
+// [database/sql.Scanner].
 type RowsColumnScanner interface {
 	Rows