Abstract the DBAdapter so that we can support other sql adapters

This was done for a few different reasons:

1. This allows us to work on top of the pgx client in the future
2. This would allow our users to implement their own DBAdapters
   to use with our tool.
3. This gives the users the option of using advanced configs
   of any sql client they want to use and just feed us with it
   after the configuration is done, which means we will not have
   to worry about supporting a growing number of configurations
   as we try to add support to more drivers or if we get issues
   asking for more advanced config options.

README.md

@@ -523,11 +523,15 @@ make test
 
 - Add tests for tables using composite keys
 - Add support for serializing structs as other formats such as YAML
-- Update `kstructs.FillStructWith` to work with `json` tagged attributes
+- Update `kstructs.FillStructWith` to work with `ksql:"..,json"` tagged attributes
 - Make testing easier by exposing the connection strings in an .env file
 - Make testing easier by automatically creating the `ksql` database
 - Create a way for users to submit user defined dialects
 - Improve error messages
+- Add support for the update function to work with maps for partial updates
+- Add support for the insert function to work with maps
+- Add support for a `ksql.Array(params ...interface{})` for allowing queries like this:
+  `db.Query(ctx, &user, "SELECT * FROM user WHERE id in (?)", ksql.Array(1,2,3))`
 
 ### Optimization Oportunities
 

adapters.go

@@ -0,0 +1,47 @@
+package ksql
+
+import (
+	"context"
+	"database/sql"
+)
+
+// SQLAdapter adapts the sql.DB type to be compatible with the `DBAdapter` interface
+type SQLAdapter struct {
+	*sql.DB
+}
+
+var _ DBAdapter = SQLAdapter{}
+
+// ExecContext implements the DBAdapter interface
+func (s SQLAdapter) ExecContext(ctx context.Context, query string, args ...interface{}) (Result, error) {
+	return s.DB.ExecContext(ctx, query, args...)
+}
+
+// QueryContext implements the DBAdapter interface
+func (s SQLAdapter) QueryContext(ctx context.Context, query string, args ...interface{}) (Rows, error) {
+	return s.DB.QueryContext(ctx, query, args...)
+}
+
+// SQLTx is used to implement the DBAdapter interface and implements
+// the Tx interface
+type SQLTx struct {
+	*sql.Tx
+}
+
+// ExecContext implements the Tx interface
+func (s SQLTx) ExecContext(ctx context.Context, query string, args ...interface{}) (Result, error) {
+	return s.Tx.ExecContext(ctx, query, args...)
+}
+
+// QueryContext implements the Tx interface
+func (s SQLTx) QueryContext(ctx context.Context, query string, args ...interface{}) (Rows, error) {
+	return s.Tx.QueryContext(ctx, query, args...)
+}
+
+var _ Tx = SQLTx{}
+
+// BeginTx implements the Tx interface
+func (s SQLAdapter) BeginTx(ctx context.Context) (Tx, error) {
+	tx, err := s.DB.BeginTx(ctx, nil)
+	return SQLTx{Tx: tx}, err
+}

ksql.go

@@ -35,8 +35,36 @@ type DB struct {
 //
 // To create a new client using this adapter use ksql.NewWithDB()
 type DBAdapter interface {
-	ExecContext(ctx context.Context, query string, args ...interface{}) (sql.Result, error)
-	QueryContext(ctx context.Context, query string, args ...interface{}) (*sql.Rows, error)
+	ExecContext(ctx context.Context, query string, args ...interface{}) (Result, error)
+	QueryContext(ctx context.Context, query string, args ...interface{}) (Rows, error)
+}
+
+// TxBeginner needs to be implemented by the DBAdapter in order to make it possible
+// to use the `ksql.Transaction()` function.
+type TxBeginner interface {
+	BeginTx(ctx context.Context) (Tx, error)
+}
+
+// Result stores information about the result of an Exec query
+type Result = sql.Result
+
+// Rows represents the results from a call to Query()
+type Rows interface {
+	Scan(...interface{}) error
+	Close() error
+	Next() bool
+	Err() error
+	Columns() ([]string, error)
+}
+
+var _ Rows = &sql.Rows{}
+
+// Tx represents a transaction and is expected to be returned by the DBAdapter.BeginTx function
+type Tx interface {
+	ExecContext(ctx context.Context, query string, args ...interface{}) (Result, error)
+	QueryContext(ctx context.Context, query string, args ...interface{}) (Rows, error)
+	Rollback() error
+	Commit() error
 }
 
 // Config describes the optional arguments accepted
@@ -66,7 +94,7 @@ func New(
 
 	db.SetMaxOpenConns(config.MaxOpenConns)
 
-	return newWithDB(db, dbDriver, connectionString)
+	return newWithDB(SQLAdapter{db}, dbDriver, connectionString)
 }
 
 // NewWithDB allows the user to insert a custom implementation
@@ -752,11 +780,11 @@ func (c DB) Exec(ctx context.Context, query string, params ...interface{}) error
 
 // Transaction just runs an SQL command on the database returning no rows.
 func (c DB) Transaction(ctx context.Context, fn func(Provider) error) error {
-	switch db := c.db.(type) {
-	case *sql.Tx:
+	switch txBeginner := c.db.(type) {
+	case Tx:
 		return fn(c)
-	case *sql.DB:
-		tx, err := db.BeginTx(ctx, nil)
+	case TxBeginner:
+		tx, err := txBeginner.BeginTx(ctx)
 		if err != nil {
 			return err
 		}
@@ -789,7 +817,7 @@ func (c DB) Transaction(ctx context.Context, fn func(Provider) error) error {
 		return tx.Commit()
 
 	default:
-		return fmt.Errorf("unexpected error on ksql: db attribute has an invalid type")
+		return fmt.Errorf("can't start transaction: The DBAdapter doesn't implement the TxBegginner interface")
 	}
 }
 
@@ -801,7 +829,7 @@ func (nopScanner) Scan(value interface{}) error {
 	return nil
 }
 
-func scanRows(dialect dialect, rows *sql.Rows, record interface{}) error {
+func scanRows(dialect dialect, rows Rows, record interface{}) error {
 	v := reflect.ValueOf(record)
 	t := v.Type()
 	if t.Kind() != reflect.Ptr {
@@ -836,7 +864,7 @@ func scanRows(dialect dialect, rows *sql.Rows, record interface{}) error {
 	return rows.Scan(scanArgs...)
 }
 
-func getScanArgsForNestedStructs(dialect dialect, rows *sql.Rows, t reflect.Type, v reflect.Value, info kstructs.StructInfo) []interface{} {
+func getScanArgsForNestedStructs(dialect dialect, rows Rows, t reflect.Type, v reflect.Value, info kstructs.StructInfo) []interface{} {
 	scanArgs := []interface{}{}
 	for i := 0; i < v.NumField(); i++ {
 		// TODO(vingarcia00): Handle case where type is pointer

ksql_test.go

@@ -687,7 +687,7 @@ func TestInsert(t *testing.T) {
 					assert.Equal(t, nil, err)
 
 					var inserted User
-					err := getUserByName(db, c.dialect, &inserted, "Preset Name")
+					err := getUserByName(SQLAdapter{db}, c.dialect, &inserted, "Preset Name")
 					assert.Equal(t, nil, err)
 					assert.Equal(t, 5455, inserted.Age)
 				})
@@ -792,7 +792,7 @@ func TestInsert(t *testing.T) {
 					assert.Equal(t, nil, err)
 
 					var u User
-					err = getUserByName(db, c.dialect, &u, "Inserted With no ID")
+					err = getUserByName(SQLAdapter{db}, c.dialect, &u, "Inserted With no ID")
 					assert.Equal(t, nil, err)
 					assert.NotEqual(t, uint(0), u.ID)
 					assert.Equal(t, 42, u.Age)
@@ -1944,7 +1944,7 @@ func newTestDB(db *sql.DB, driver string) DB {
 	return DB{
 		driver:  driver,
 		dialect: supportedDialects[driver],
-		db:      db,
+		db:      SQLAdapter{db},
 	}
 }
 
@@ -1968,7 +1968,7 @@ func shiftErrSlice(errs *[]error) error {
 }
 
 func getUsersByID(dbi DBAdapter, dialect dialect, resultsPtr *[]User, ids ...uint) error {
-	db := dbi.(*sql.DB)
+	db := dbi.(SQLAdapter)
 
 	placeholders := make([]string, len(ids))
 	params := make([]interface{}, len(ids))
@@ -1978,7 +1978,7 @@ func getUsersByID(dbi DBAdapter, dialect dialect, resultsPtr *[]User, ids ...uin
 	}
 
 	results := []User{}
-	rows, err := db.Query(
+	rows, err := db.DB.Query(
 		fmt.Sprintf(
 			"SELECT id, name, age FROM users WHERE id IN (%s)",
 			strings.Join(placeholders, ", "),
@@ -2010,9 +2010,9 @@ func getUsersByID(dbi DBAdapter, dialect dialect, resultsPtr *[]User, ids ...uin
 }
 
 func getUserByID(dbi DBAdapter, dialect dialect, result *User, id uint) error {
-	db := dbi.(*sql.DB)
+	db := dbi.(SQLAdapter)
 
-	row := db.QueryRow(`SELECT id, name, age, address FROM users WHERE id=`+dialect.Placeholder(0), id)
+	row := db.DB.QueryRow(`SELECT id, name, age, address FROM users WHERE id=`+dialect.Placeholder(0), id)
 	if row.Err() != nil {
 		return row.Err()
 	}
@@ -2031,9 +2031,9 @@ func getUserByID(dbi DBAdapter, dialect dialect, result *User, id uint) error {
 }
 
 func getUserByName(dbi DBAdapter, dialect dialect, result *User, name string) error {
-	db := dbi.(*sql.DB)
+	db := dbi.(SQLAdapter)
 
-	row := db.QueryRow(`SELECT id, name, age, address FROM users WHERE name=`+dialect.Placeholder(0), name)
+	row := db.DB.QueryRow(`SELECT id, name, age, address FROM users WHERE name=`+dialect.Placeholder(0), name)
 	if row.Err() != nil {
 		return row.Err()
 	}