Support AUTOINCREMENT directive in SQLite (#936)

* refactor: delegate autoincrement to dialects

* feat: support AUTOINCREMENT PKs in SQLite

* chore: use succinct syntax

* refactor: push the check for PK to the caller

#929

dialect/mssqldialect/dialect.go

@@ -137,6 +137,10 @@ func (d *Dialect) DefaultVarcharLen() int {
 	return 255
 }
 
+func (d *Dialect) AppendSequence(b []byte, _ *schema.Table, _ *schema.Field) []byte {
+	return append(b, " IDENTITY"...)
+}
+
 func sqlType(field *schema.Field) string {
 	switch field.DiscoveredSQLType {
 	case sqltype.Timestamp:

dialect/mysqldialect/dialect.go

@@ -180,6 +180,10 @@ func (d *Dialect) DefaultVarcharLen() int {
 	return 255
 }
 
+func (d *Dialect) AppendSequence(b []byte, _ *schema.Table, _ *schema.Field) []byte {
+	return append(b, " AUTO_INCREMENT"...)
+}
+
 func sqlType(field *schema.Field) string {
 	if field.DiscoveredSQLType == sqltype.Timestamp {
 		return datetimeType

dialect/pgdialect/dialect.go

@@ -108,3 +108,7 @@ func (d *Dialect) AppendUint32(b []byte, n uint32) []byte {
 func (d *Dialect) AppendUint64(b []byte, n uint64) []byte {
 	return strconv.AppendInt(b, int64(n), 10)
 }
+
+func (d *Dialect) AppendSequence(b []byte, _ *schema.Table, _ *schema.Field) []byte {
+	return append(b, " GENERATED BY DEFAULT AS IDENTITY"...)
+}

dialect/sqlitedialect/dialect.go

@@ -39,6 +39,7 @@ func New() *Dialect {
 		feature.InsertOnConflict |
 		feature.TableNotExists |
 		feature.SelectExists |
+		feature.AutoIncrement |
 		feature.CompositeIn
 	return d
 }
@@ -91,6 +92,25 @@ func (d *Dialect) DefaultVarcharLen() int {
 	return 0
 }
 
+// AppendSequence adds AUTOINCREMENT keyword to the column definition. As per [documentation],
+// AUTOINCREMENT is only valid for INTEGER PRIMARY KEY, and this method will be a noop for other columns.
+//
+// Because this is a valid construct:
+//	CREATE TABLE ("id" INTEGER PRIMARY KEY AUTOINCREMENT);
+// and this is not:
+//	CREATE TABLE ("id" INTEGER AUTOINCREMENT, PRIMARY KEY ("id"));
+// AppendSequence adds a primary key constraint as a *side-effect*. Callers should expect it to avoid building invalid SQL.
+// SQLite also [does not support] AUTOINCREMENT column in composite primary keys.
+//
+// [documentation]: https://www.sqlite.org/autoinc.html
+// [does not support]: https://stackoverflow.com/a/6793274/14726116
+func (d *Dialect) AppendSequence(b []byte, table *schema.Table, field *schema.Field) []byte {
+	if field.IsPK && len(table.PKs) == 1 && field.CreateTableSQLType == sqltype.Integer {
+		b = append(b, " PRIMARY KEY AUTOINCREMENT"...)
+	}
+	return b
+}
+
 func fieldSQLType(field *schema.Field) string {
 	switch field.DiscoveredSQLType {
 	case sqltype.SmallInt, sqltype.BigInt:

internal/dbtest/testdata/snapshots/TestQuery-sqlite-102

@@ -1 +1 @@
-CREATE TABLE "models" ("id" INTEGER NOT NULL, "str" VARCHAR, PRIMARY KEY ("id")) PARTITION BY HASH (id)
+CREATE TABLE "models" ("id" INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, "str" VARCHAR) PARTITION BY HASH (id)

internal/dbtest/testdata/snapshots/TestQuery-sqlite-103

@@ -1 +1 @@
-CREATE TABLE "models" ("id" INTEGER NOT NULL, "str" VARCHAR, PRIMARY KEY ("id")) TABLESPACE "fasttablespace"
+CREATE TABLE "models" ("id" INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, "str" VARCHAR) TABLESPACE "fasttablespace"

internal/dbtest/testdata/snapshots/TestQuery-sqlite-151

@@ -1 +1 @@
-CREATE TABLE "users" ("id" INTEGER NOT NULL, PRIMARY KEY ("id"))
+CREATE TABLE "users" ("id" INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT)

internal/dbtest/testdata/snapshots/TestQuery-sqlite-32

@@ -1 +1 @@
-CREATE TABLE "models" ("id" INTEGER NOT NULL, "str" VARCHAR, PRIMARY KEY ("id"))
+CREATE TABLE "models" ("id" INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, "str" VARCHAR)

internal/dbtest/testdata/snapshots/TestQuery-sqlite-33

@@ -1 +1 @@
-CREATE TABLE "models" ("id" INTEGER NOT NULL, "struct" VARCHAR, "map" VARCHAR, "slice" VARCHAR, "array" VARCHAR, PRIMARY KEY ("id"))
+CREATE TABLE "models" ("id" INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, "struct" VARCHAR, "map" VARCHAR, "slice" VARCHAR, "array" VARCHAR)

internal/dbtest/testdata/snapshots/TestQuery-sqlite-57

@@ -1 +1 @@
-CREATE TABLE "models" ("id" INTEGER NOT NULL, "str" VARCHAR, PRIMARY KEY ("id"), FOREIGN KEY ("profile_id") REFERENCES "profiles" ("id"))
+CREATE TABLE "models" ("id" INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, "str" VARCHAR, FOREIGN KEY ("profile_id") REFERENCES "profiles" ("id"))

internal/dbtest/testdata/snapshots/TestQuery-sqlite-71

@@ -1 +1 @@
-CREATE TABLE "models" ("id" INTEGER NOT NULL, PRIMARY KEY ("id"))
+CREATE TABLE "models" ("id" INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT)

query_table_create.go

@@ -1,6 +1,7 @@
 package bun
 
 import (
+	"bytes"
 	"context"
 	"database/sql"
 	"fmt"
@@ -146,7 +147,7 @@ func (q *CreateTableQuery) AppendQuery(fmter schema.Formatter, b []byte) (_ []by
 		b = append(b, "TEMP "...)
 	}
 	b = append(b, "TABLE "...)
-	if q.ifNotExists && fmter.Dialect().Features().Has(feature.TableNotExists) {
+	if q.ifNotExists && fmter.HasFeature(feature.TableNotExists) {
 		b = append(b, "IF NOT EXISTS "...)
 	}
 	b, err = q.appendFirstTable(fmter, b)
@@ -167,19 +168,12 @@ func (q *CreateTableQuery) AppendQuery(fmter schema.Formatter, b []byte) (_ []by
 		if field.NotNull {
 			b = append(b, " NOT NULL"...)
 		}
-		if field.AutoIncrement {
-			switch {
-			case fmter.Dialect().Features().Has(feature.AutoIncrement):
-				b = append(b, " AUTO_INCREMENT"...)
-			case fmter.Dialect().Features().Has(feature.Identity):
-				b = append(b, " IDENTITY"...)
-			}
-		}
-		if field.Identity {
-			if fmter.Dialect().Features().Has(feature.GeneratedIdentity) {
-				b = append(b, " GENERATED BY DEFAULT AS IDENTITY"...)
-			}
+
+		if (field.Identity && fmter.HasFeature(feature.GeneratedIdentity)) ||
+			(field.AutoIncrement && (fmter.HasFeature(feature.AutoIncrement) || fmter.HasFeature(feature.Identity))) {
+			b = q.db.dialect.AppendSequence(b, q.table, field)
 		}
+
 		if field.SQLDefault != "" {
 			b = append(b, " DEFAULT "...)
 			b = append(b, field.SQLDefault...)
@@ -199,7 +193,12 @@ func (q *CreateTableQuery) AppendQuery(fmter schema.Formatter, b []byte) (_ []by
 		}
 	}
 
-	b = q.appendPKConstraint(b, q.table.PKs)
+	// In SQLite AUTOINCREMENT is only valid for INTEGER PRIMARY KEY columns, so it might be that
+	// a primary key constraint has already been created in dialect.AppendSequence() call above.
+	// See sqldialect.Dialect.AppendSequence() for more details.
+	if len(q.table.PKs) > 0 && !bytes.Contains(b, []byte("PRIMARY KEY")) {
+		b = q.appendPKConstraint(b, q.table.PKs)
+	}
 	b = q.appendUniqueConstraints(fmter, b)
 
 	if q.fksFromRel {
@@ -330,10 +329,6 @@ func (q *CreateTableQuery) appendFKConstraints(
 }
 
 func (q *CreateTableQuery) appendPKConstraint(b []byte, pks []*schema.Field) []byte {
-	if len(pks) == 0 {
-		return b
-	}
-
 	b = append(b, ", PRIMARY KEY ("...)
 	b = appendColumns(b, "", pks)
 	b = append(b, ")"...)

schema/dialect.go

@@ -31,6 +31,10 @@ type Dialect interface {
 	AppendJSON(b, jsonb []byte) []byte
 	AppendBool(b []byte, v bool) []byte
 
+	// AppendSequence adds the appropriate instruction for the driver to create a sequence
+	// from which (autoincremented) values for the column will be generated.
+	AppendSequence(b []byte, t *Table, f *Field) []byte
+
 	// DefaultVarcharLen should be returned for dialects in which specifying VARCHAR length
 	// is mandatory in queries that modify the schema (CREATE TABLE / ADD COLUMN, etc).
 	// Dialects that do not have such requirement may return 0, which should be interpreted so by the caller.
@@ -177,3 +181,7 @@ func (d *nopDialect) IdentQuote() byte {
 func (d *nopDialect) DefaultVarcharLen() int {
 	return 0
 }
+
+func (d *nopDialect) AppendSequence(b []byte, _ *Table, _ *Field) []byte {
+	return b
+}