jinzhu/gorm

package mssql

import (
    "database/sql/driver"
    "encoding/json"
    "errors"
    "fmt"
    "reflect"
    "strconv"
    "strings"
    "time"

    // Importing mssql driver package only in dialect file, otherwide not needed
    _ "github.com/denisenkom/go-mssqldb"
    "github.com/jinzhu/gorm"
)

func setIdentityInsert(scope *gorm.Scope) {
    if scope.Dialect().GetName() == "mssql" {
        for _, field := range scope.PrimaryFields() {
            if _, ok := field.TagSettingsGet("AUTO_INCREMENT"); ok && !field.IsBlank {
                scope.NewDB().Exec(fmt.Sprintf("SET IDENTITY_INSERT %v ON", scope.TableName()))
                scope.InstanceSet("mssql:identity_insert_on", true)
            }
        }
    }
}

func turnOffIdentityInsert(scope *gorm.Scope) {
    if scope.Dialect().GetName() == "mssql" {
        if _, ok := scope.InstanceGet("mssql:identity_insert_on"); ok {
            scope.NewDB().Exec(fmt.Sprintf("SET IDENTITY_INSERT %v OFF", scope.TableName()))
        }
    }
}

func init() {
    gorm.DefaultCallback.Create().After("gorm:begin_transaction").Register("mssql:set_identity_insert", setIdentityInsert)
    gorm.DefaultCallback.Create().Before("gorm:commit_or_rollback_transaction").Register("mssql:turn_off_identity_insert", turnOffIdentityInsert)
    gorm.RegisterDialect("mssql", &mssql{})
}

type mssql struct {
    db gorm.SQLCommon
    gorm.DefaultForeignKeyNamer
}

func (mssql) GetName() string {
    return "mssql"
}

func (s *mssql) SetDB(db gorm.SQLCommon) {
    s.db = db
}

func (mssql) BindVar(i int) string {
    return "$$$" // ?
}

func (mssql) Quote(key string) string {
    return fmt.Sprintf(`[%s]`, key)
}

func (s *mssql) DataTypeOf(field *gorm.StructField) string {
    var dataValue, sqlType, size, additionalType = gorm.ParseFieldStructForDialect(field, s)

    if sqlType == "" {
        switch dataValue.Kind() {
        case reflect.Bool:
            sqlType = "bit"
        case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uintptr:
            if s.fieldCanAutoIncrement(field) {
                field.TagSettingsSet("AUTO_INCREMENT", "AUTO_INCREMENT")
                sqlType = "int IDENTITY(1,1)"
            } else {
                sqlType = "int"
            }
        case reflect.Int64, reflect.Uint64:
            if s.fieldCanAutoIncrement(field) {
                field.TagSettingsSet("AUTO_INCREMENT", "AUTO_INCREMENT")
                sqlType = "bigint IDENTITY(1,1)"
            } else {
                sqlType = "bigint"
            }
        case reflect.Float32, reflect.Float64:
            sqlType = "float"
        case reflect.String:
            if size > 0 && size < 8000 {
                sqlType = fmt.Sprintf("nvarchar(%d)", size)
            } else {
                sqlType = "nvarchar(max)"
            }
        case reflect.Struct:
            if _, ok := dataValue.Interface().(time.Time); ok {
                sqlType = "datetimeoffset"
            }
        default:
            if gorm.IsByteArrayOrSlice(dataValue) {
                if size > 0 && size < 8000 {
                    sqlType = fmt.Sprintf("varbinary(%d)", size)
                } else {
                    sqlType = "varbinary(max)"
                }
            }
        }
    }

    if sqlType == "" {
        panic(fmt.Sprintf("invalid sql type %s (%s) for mssql", dataValue.Type().Name(), dataValue.Kind().String()))
    }

    if strings.TrimSpace(additionalType) == "" {
        return sqlType
    }
    return fmt.Sprintf("%v %v", sqlType, additionalType)
}

func (s mssql) fieldCanAutoIncrement(field *gorm.StructField) bool {
    if value, ok := field.TagSettingsGet("AUTO_INCREMENT"); ok {
        return value != "FALSE"
    }
    return field.IsPrimaryKey
}

func (s mssql) HasIndex(tableName string, indexName string) bool {
    var count int
    s.db.QueryRow("SELECT count(*) FROM sys.indexes WHERE name=? AND object_id=OBJECT_ID(?)", indexName, tableName).Scan(&count)
    return count > 0
}

func (s mssql) RemoveIndex(tableName string, indexName string) error {
    _, err := s.db.Exec(fmt.Sprintf("DROP INDEX %v ON %v", indexName, s.Quote(tableName)))
    return err
}

func (s mssql) HasForeignKey(tableName string, foreignKeyName string) bool {
    var count int
    currentDatabase, tableName := currentDatabaseAndTable(&s, tableName)
    s.db.QueryRow(`SELECT count(*) 
    FROM sys.foreign_keys as F inner join sys.tables as T on F.parent_object_id=T.object_id 
        inner join information_schema.tables as I on I.TABLE_NAME = T.name 
    WHERE F.name = ? 
        AND T.Name = ? AND I.TABLE_CATALOG = ?;`, foreignKeyName, tableName, currentDatabase).Scan(&count)
    return count > 0
}

func (s mssql) HasTable(tableName string) bool {
    var count int
    currentDatabase, tableName := currentDatabaseAndTable(&s, tableName)
    s.db.QueryRow("SELECT count(*) FROM INFORMATION_SCHEMA.tables WHERE table_name = ? AND table_catalog = ?", tableName, currentDatabase).Scan(&count)
    return count > 0
}

func (s mssql) HasColumn(tableName string, columnName string) bool {
    var count int
    currentDatabase, tableName := currentDatabaseAndTable(&s, tableName)
    s.db.QueryRow("SELECT count(*) FROM information_schema.columns WHERE table_catalog = ? AND table_name = ? AND column_name = ?", currentDatabase, tableName, columnName).Scan(&count)
    return count > 0
}

func (s mssql) ModifyColumn(tableName string, columnName string, typ string) error {
    _, err := s.db.Exec(fmt.Sprintf("ALTER TABLE %v ALTER COLUMN %v %v", tableName, columnName, typ))
    return err
}

func (s mssql) CurrentDatabase() (name string) {
    s.db.QueryRow("SELECT DB_NAME() AS [Current Database]").Scan(&name)
    return
}

func parseInt(value interface{}) (int64, error) {
    return strconv.ParseInt(fmt.Sprint(value), 0, 0)
}

func (mssql) LimitAndOffsetSQL(limit, offset interface{}) (sql string, err error) {
    if offset != nil {
        if parsedOffset, err := parseInt(offset); err != nil {
            return "", err
        } else if parsedOffset >= 0 {
            sql += fmt.Sprintf(" OFFSET %d ROWS", parsedOffset)
        }
    }
    if limit != nil {
        if parsedLimit, err := parseInt(limit); err != nil {
            return "", err
        } else if parsedLimit >= 0 {
            if sql == "" {
                // add default zero offset
                sql += " OFFSET 0 ROWS"
            }
            sql += fmt.Sprintf(" FETCH NEXT %d ROWS ONLY", parsedLimit)
        }
    }
    return
}

func (mssql) SelectFromDummyTable() string {
    return ""
}

func (mssql) LastInsertIDOutputInterstitial(tableName, columnName string, columns []string) string {
    if len(columns) == 0 {
        // No OUTPUT to query
        return ""
    }
    return fmt.Sprintf("OUTPUT Inserted.%v", columnName)
}

func (mssql) LastInsertIDReturningSuffix(tableName, columnName string) string {
    // https://stackoverflow.com/questions/5228780/how-to-get-last-inserted-id
    return "; SELECT SCOPE_IDENTITY()"
}

func (mssql) DefaultValueStr() string {
    return "DEFAULT VALUES"
}

// NormalizeIndexAndColumn returns argument's index name and column name without doing anything
func (mssql) NormalizeIndexAndColumn(indexName, columnName string) (string, string) {
    return indexName, columnName
}

func currentDatabaseAndTable(dialect gorm.Dialect, tableName string) (string, string) {
    if strings.Contains(tableName, ".") {
        splitStrings := strings.SplitN(tableName, ".", 2)
        return splitStrings[0], splitStrings[1]
    }
    return dialect.CurrentDatabase(), tableName
}

// JSON type to support easy handling of JSON data in character table fields
// using golang json.RawMessage for deferred decoding/encoding
type JSON struct {
    json.RawMessage
}

// Value get value of JSON
func (j JSON) Value() (driver.Value, error) {
    if len(j.RawMessage) == 0 {
        return nil, nil
    }
    return j.MarshalJSON()
}

// Scan scan value into JSON
func (j *JSON) Scan(value interface{}) error {
    str, ok := value.(string)
    if !ok {
        return errors.New(fmt.Sprint("Failed to unmarshal JSONB value (strcast):", value))
    }
    bytes := []byte(str)
    return json.Unmarshal(bytes, j)
}