From c42104eb2ffb3a6904625e123c46cfcce7674e51 Mon Sep 17 00:00:00 2001
From: xen0l <1426772+xen0l@users.noreply.github.com>
Date: Sat, 24 Oct 2026 21:57:51 +0000
Subject: [PATCH] fix(duckdb): rewrite sqlc.arg and @name to native
 placeholders

The preprocess dialect table had no entry for DuckDB, and an engine with
no entry gets its source back unchanged. sqlc.arg(), sqlc.narg() and
@name then reached the analyzer as function calls and column names.

Add a DuckDB entry that uses $1 placeholders.

Reject sqlc.slice for this dialect. With $1 placeholders the generated Go
still calls strings.Replace on a "?" marker that the SQL does not
contain, so it binds only the first element of the list and returns wrong
rows without an error. A list parameter (list_contains or ANY) is the
DuckDB way to do this.

Adds the duckdb_named_params and analyze_slice_rejected cases.
---
 .../analyze_slice_rejected/duckdb/exec.json   |   5 +
 .../analyze_slice_rejected/duckdb/query.sql   |   2 +
 .../analyze_slice_rejected/duckdb/schema.sql  |   1 +
 .../analyze_slice_rejected/duckdb/stderr.txt  |   1 +
 .../duckdb_named_params/duckdb/exec.json      |   1 +
 .../duckdb_named_params/duckdb/go/db.go       |  31 +++++
 .../duckdb_named_params/duckdb/go/models.go   |  10 ++
 .../duckdb/go/query.sql.go                    | 124 ++++++++++++++++++
 .../duckdb_named_params/duckdb/query.sql      |  11 ++
 .../duckdb_named_params/duckdb/schema.sql     |   1 +
 .../duckdb_named_params/duckdb/sqlc.yaml      |  10 ++
 internal/sql/preprocess/CLAUDE.md             |   1 +
 internal/sql/preprocess/dialect.go            |  15 +++
 internal/sql/preprocess/scan.go               |   7 +
 14 files changed, 220 insertions(+)
 create mode 100644 internal/endtoend/testdata/analyze_slice_rejected/duckdb/exec.json
 create mode 100644 internal/endtoend/testdata/analyze_slice_rejected/duckdb/query.sql
 create mode 100644 internal/endtoend/testdata/analyze_slice_rejected/duckdb/schema.sql
 create mode 100644 internal/endtoend/testdata/analyze_slice_rejected/duckdb/stderr.txt
 create mode 100644 internal/endtoend/testdata/duckdb_named_params/duckdb/exec.json
 create mode 100644 internal/endtoend/testdata/duckdb_named_params/duckdb/go/db.go
 create mode 100644 internal/endtoend/testdata/duckdb_named_params/duckdb/go/models.go
 create mode 100644 internal/endtoend/testdata/duckdb_named_params/duckdb/go/query.sql.go
 create mode 100644 internal/endtoend/testdata/duckdb_named_params/duckdb/query.sql
 create mode 100644 internal/endtoend/testdata/duckdb_named_params/duckdb/schema.sql
 create mode 100644 internal/endtoend/testdata/duckdb_named_params/duckdb/sqlc.yaml

diff --git a/internal/endtoend/testdata/analyze_slice_rejected/duckdb/exec.json b/internal/endtoend/testdata/analyze_slice_rejected/duckdb/exec.json
new file mode 100644
index 0000000000..56cb4b3fff
--- /dev/null
+++ b/internal/endtoend/testdata/analyze_slice_rejected/duckdb/exec.json
@@ -0,0 +1,5 @@
+{
+  "command": "analyze",
+  "args": ["--dialect", "duckdb", "--schema", "schema.sql", "query.sql"],
+  "contexts": ["base"]
+}
diff --git a/internal/endtoend/testdata/analyze_slice_rejected/duckdb/query.sql b/internal/endtoend/testdata/analyze_slice_rejected/duckdb/query.sql
new file mode 100644
index 0000000000..d89f625b0a
--- /dev/null
+++ b/internal/endtoend/testdata/analyze_slice_rejected/duckdb/query.sql
@@ -0,0 +1,2 @@
+-- name: ByIDs :many
+SELECT id, name FROM items WHERE id IN (sqlc.slice(ids));
diff --git a/internal/endtoend/testdata/analyze_slice_rejected/duckdb/schema.sql b/internal/endtoend/testdata/analyze_slice_rejected/duckdb/schema.sql
new file mode 100644
index 0000000000..3a1848aa23
--- /dev/null
+++ b/internal/endtoend/testdata/analyze_slice_rejected/duckdb/schema.sql
@@ -0,0 +1 @@
+CREATE TABLE items (id INTEGER NOT NULL, name VARCHAR NOT NULL);
diff --git a/internal/endtoend/testdata/analyze_slice_rejected/duckdb/stderr.txt b/internal/endtoend/testdata/analyze_slice_rejected/duckdb/stderr.txt
new file mode 100644
index 0000000000..ab1167afc9
--- /dev/null
+++ b/internal/endtoend/testdata/analyze_slice_rejected/duckdb/stderr.txt
@@ -0,0 +1 @@
+Error: error parsing queries: query.sql:2:41: sqlc.slice is not supported by this engine; bind a list parameter instead
diff --git a/internal/endtoend/testdata/duckdb_named_params/duckdb/exec.json b/internal/endtoend/testdata/duckdb_named_params/duckdb/exec.json
new file mode 100644
index 0000000000..f4e21983b6
--- /dev/null
+++ b/internal/endtoend/testdata/duckdb_named_params/duckdb/exec.json
@@ -0,0 +1 @@
+{"contexts": ["base"]}
diff --git a/internal/endtoend/testdata/duckdb_named_params/duckdb/go/db.go b/internal/endtoend/testdata/duckdb_named_params/duckdb/go/db.go
new file mode 100644
index 0000000000..32faa9f2b8
--- /dev/null
+++ b/internal/endtoend/testdata/duckdb_named_params/duckdb/go/db.go
@@ -0,0 +1,31 @@
+// Code generated by sqlc. DO NOT EDIT.
+// versions:
+//   sqlc v1.31.1
+
+package querytest
+
+import (
+	"context"
+	"database/sql"
+)
+
+type DBTX interface {
+	ExecContext(context.Context, string, ...any) (sql.Result, error)
+	PrepareContext(context.Context, string) (*sql.Stmt, error)
+	QueryContext(context.Context, string, ...any) (*sql.Rows, error)
+	QueryRowContext(context.Context, string, ...any) *sql.Row
+}
+
+func New(db DBTX) *Queries {
+	return &Queries{db: db}
+}
+
+type Queries struct {
+	db DBTX
+}
+
+func (q *Queries) WithTx(tx *sql.Tx) *Queries {
+	return &Queries{
+		db: tx,
+	}
+}
diff --git a/internal/endtoend/testdata/duckdb_named_params/duckdb/go/models.go b/internal/endtoend/testdata/duckdb_named_params/duckdb/go/models.go
new file mode 100644
index 0000000000..66124a32e6
--- /dev/null
+++ b/internal/endtoend/testdata/duckdb_named_params/duckdb/go/models.go
@@ -0,0 +1,10 @@
+// Code generated by sqlc. DO NOT EDIT.
+// versions:
+//   sqlc v1.31.1
+
+package querytest
+
+type Item struct {
+	ID   int32
+	Name string
+}
diff --git a/internal/endtoend/testdata/duckdb_named_params/duckdb/go/query.sql.go b/internal/endtoend/testdata/duckdb_named_params/duckdb/go/query.sql.go
new file mode 100644
index 0000000000..cc8b35bb19
--- /dev/null
+++ b/internal/endtoend/testdata/duckdb_named_params/duckdb/go/query.sql.go
@@ -0,0 +1,124 @@
+// Code generated by sqlc. DO NOT EDIT.
+// versions:
+//   sqlc v1.31.1
+// source: query.sql
+
+package querytest
+
+import (
+	"context"
+	"database/sql"
+)
+
+const byAt = `-- name: ByAt :many
+SELECT id, name FROM items WHERE id = $1;
+`
+
+func (q *Queries) ByAt(ctx context.Context, wantID int32) ([]Item, error) {
+	rows, err := q.db.QueryContext(ctx, byAt, wantID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []Item
+	for rows.Next() {
+		var i Item
+		if err := rows.Scan(&i.ID, &i.Name); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Close(); err != nil {
+		return nil, err
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
+const byID = `-- name: ByID :many
+SELECT id, name FROM items WHERE id = $1;
+`
+
+func (q *Queries) ByID(ctx context.Context, wantID int32) ([]Item, error) {
+	rows, err := q.db.QueryContext(ctx, byID, wantID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []Item
+	for rows.Next() {
+		var i Item
+		if err := rows.Scan(&i.ID, &i.Name); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Close(); err != nil {
+		return nil, err
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
+const byNullableID = `-- name: ByNullableID :many
+SELECT id, name FROM items WHERE id = $1;
+`
+
+func (q *Queries) ByNullableID(ctx context.Context, wantID sql.NullInt32) ([]Item, error) {
+	rows, err := q.db.QueryContext(ctx, byNullableID, wantID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []Item
+	for rows.Next() {
+		var i Item
+		if err := rows.Scan(&i.ID, &i.Name); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Close(); err != nil {
+		return nil, err
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
+const range_ = `-- name: Range :many
+SELECT id, name FROM items WHERE id > $1 AND id < $2;
+`
+
+type RangeParams struct {
+	MinID int32
+	MaxID int32
+}
+
+func (q *Queries) Range(ctx context.Context, arg RangeParams) ([]Item, error) {
+	rows, err := q.db.QueryContext(ctx, range_, arg.MinID, arg.MaxID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []Item
+	for rows.Next() {
+		var i Item
+		if err := rows.Scan(&i.ID, &i.Name); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Close(); err != nil {
+		return nil, err
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
diff --git a/internal/endtoend/testdata/duckdb_named_params/duckdb/query.sql b/internal/endtoend/testdata/duckdb_named_params/duckdb/query.sql
new file mode 100644
index 0000000000..b455352ab6
--- /dev/null
+++ b/internal/endtoend/testdata/duckdb_named_params/duckdb/query.sql
@@ -0,0 +1,11 @@
+-- name: ByID :many
+SELECT id, name FROM items WHERE id = sqlc.arg(want_id);
+
+-- name: ByNullableID :many
+SELECT id, name FROM items WHERE id = sqlc.narg(want_id);
+
+-- name: ByAt :many
+SELECT id, name FROM items WHERE id = @want_id;
+
+-- name: Range :many
+SELECT id, name FROM items WHERE id > sqlc.arg(min_id) AND id < sqlc.arg(max_id);
diff --git a/internal/endtoend/testdata/duckdb_named_params/duckdb/schema.sql b/internal/endtoend/testdata/duckdb_named_params/duckdb/schema.sql
new file mode 100644
index 0000000000..3a1848aa23
--- /dev/null
+++ b/internal/endtoend/testdata/duckdb_named_params/duckdb/schema.sql
@@ -0,0 +1 @@
+CREATE TABLE items (id INTEGER NOT NULL, name VARCHAR NOT NULL);
diff --git a/internal/endtoend/testdata/duckdb_named_params/duckdb/sqlc.yaml b/internal/endtoend/testdata/duckdb_named_params/duckdb/sqlc.yaml
new file mode 100644
index 0000000000..07d6d9d3b8
--- /dev/null
+++ b/internal/endtoend/testdata/duckdb_named_params/duckdb/sqlc.yaml
@@ -0,0 +1,10 @@
+version: "2"
+sql:
+  - engine: "duckdb"
+    schema: "schema.sql"
+    queries: "query.sql"
+    gen:
+      go:
+        package: "querytest"
+        out: "go"
+        sql_package: "database/sql"
diff --git a/internal/sql/preprocess/CLAUDE.md b/internal/sql/preprocess/CLAUDE.md
index a7f4d9aafe..4b15992dba 100644
--- a/internal/sql/preprocess/CLAUDE.md
+++ b/internal/sql/preprocess/CLAUDE.md
@@ -20,6 +20,7 @@ Native placeholders by dialect:
 | postgresql | `$1` | sqlc syntax |
 | mysql | `?` | user variable, left alone |
 | sqlite | `?1` | sqlc syntax |
+| duckdb | `$1` | sqlc syntax; `sqlc.slice` is rejected |
 
 GoogleSQL and ClickHouse are deliberately absent. They handle their own
 parameter syntax, so `File` returns their source unchanged and sqlc syntax is
diff --git a/internal/sql/preprocess/dialect.go b/internal/sql/preprocess/dialect.go
index 4d8d4ae85b..af7fa514d0 100644
--- a/internal/sql/preprocess/dialect.go
+++ b/internal/sql/preprocess/dialect.go
@@ -61,6 +61,12 @@ type Dialect struct {
 	// identifiers. It decides the case of a parameter named by a bare
 	// reference, e.g. sqlc.arg(FooBar).
 	FoldIdentifier bool
+
+	// NoSlice reports whether sqlc.slice is rejected. A dialect that numbers
+	// its parameters ($1) binds a list as one value, and the Go code that
+	// sqlc.slice generates only expands "?" placeholders, so it would bind
+	// the first element and return wrong rows without an error.
+	NoSlice bool
 }
 
 var dialects = map[config.Engine]Dialect{
@@ -88,6 +94,15 @@ var dialects = map[config.Engine]Dialect{
 		Backtick:  true,
 		Backslash: true,
 	},
+	// DuckDB binds with $1 like PostgreSQL and accepts $$ ... $$ strings. A
+	// bare ? is left to the engine, as it was before DuckDB had an entry.
+	config.EngineDuckDB: {
+		Style:        StyleDollar,
+		AtSign:       true,
+		DollarQuote:  true,
+		DollarNumber: true,
+		NoSlice:      true,
+	},
 	// ClickHouse binds with an unnumbered ?, like MySQL, and its identifiers
 	// keep their case.
 	config.EngineClickHouse: {
diff --git a/internal/sql/preprocess/scan.go b/internal/sql/preprocess/scan.go
index b2b4b1f534..da36627fdd 100644
--- a/internal/sql/preprocess/scan.go
+++ b/internal/sql/preprocess/scan.go
@@ -112,6 +112,13 @@ func (l *lexer) sqlcCall(start, afterSqlc int) (occurrence, int, bool) {
 	case "narg":
 		occ.kind = kindNarg
 	case "slice":
+		if l.d.NoSlice {
+			occ.err = &sqlerr.Error{
+				Message:  "sqlc.slice is not supported by this engine; bind a list parameter instead",
+				Location: start,
+			}
+			return occ, occ.end, true
+		}
 		occ.kind = kindSlice
 	case "embed":
 		occ.kind = kindEmbed