mayfly-go/server/internal/db/dbm/dbi/metadata_base.go

package dbi

import (
	"io"
	"strings"

	pq "gitee.com/liuzongyang/libpq"
	"github.com/kanzihuang/vitess/go/vt/sqlparser"
)

type BaseMetaData interface {

	// 默认库
	DefaultDb() string

	// 用于引用 SQL 标识符（关键字）的字符串
	GetIdentifierQuoteString() string

	// 引号转义，多用于sql注释转义，防止拼接sql报错，如： comment xx is '注''释'   最终注释文本为:  注'释
	QuoteEscape(str string) string

	// QuoteLiteral quotes a 'literal' (e.g. a parameter, often used to pass literal
	// to DDL and other statements that do not accept parameters) to be used as part
	// of an SQL statement.  For example:
	//
	//	exp_date := pq.QuoteLiteral("2023-01-05 15:00:00Z")
	//	err := db.Exec(fmt.Sprintf("CREATE ROLE my_user VALID UNTIL %s", exp_date))
	//
	// Any single quotes in name will be escaped. Any backslashes (i.e. "\") will be
	// replaced by two backslashes (i.e. "\\") and the C-style escape identifier
	QuoteLiteral(literal string) string

	GetSqlParserDialect() sqlparser.Dialect

	// GetColumnHelper
	GetColumnHelper() ColumnHelper

	// GetDumpHeler
	GetDumpHelper() DumpHelper
}

// 默认实现，若需要覆盖，则由各个数据库MetaData实现去覆盖重写
type DefaultMetaData struct {
}

func (dd *DefaultMetaData) DefaultDb() string {
	return ""
}

func (dd *DefaultMetaData) GetIdentifierQuoteString() string {
	return `"`
}

func (dd *DefaultMetaData) QuoteEscape(str string) string {
	return strings.Replace(str, `'`, `''`, -1)
}

func (dd *DefaultMetaData) QuoteLiteral(literal string) string {
	return pq.QuoteLiteral(literal)
}

func (dd *DefaultMetaData) GetSqlParserDialect() sqlparser.Dialect {
	return sqlparser.PostgresDialect{}
}

func (dd *DefaultMetaData) GetDumpHelper() DumpHelper {
	return new(DefaultDumpHelper)
}

func (dd *DefaultMetaData) GetColumnHelper() ColumnHelper {
	return new(DefaultColumnHelper)
}

// ColumnHelper 数据库迁移辅助方法
type ColumnHelper interface {
	// ToCommonColumn 数据库方言自带的列转换为公共列
	ToCommonColumn(dialectColumn *Column)

	// ToColumn 公共列转为各个数据库方言自带的列
	ToColumn(commonColumn *Column)

	// FixColumn 根据数据库类型修复字段长度、精度等
	FixColumn(column *Column)
}

type DefaultColumnHelper struct {
}

func (dd *DefaultColumnHelper) ToCommonColumn(dialectColumn *Column) {}

func (dd *DefaultColumnHelper) ToColumn(commonColumn *Column) {}

func (dd *DefaultColumnHelper) FixColumn(column *Column) {}

// DumpHelper 导出辅助方法
type DumpHelper interface {
	BeforeInsert(writer io.Writer, tableName string)

	BeforeInsertSql(quoteSchema string, quoteTableName string) string

	AfterInsert(writer io.Writer, tableName string, columns []Column)
}

type DefaultDumpHelper struct {
}

func (dd *DefaultDumpHelper) BeforeInsert(writer io.Writer, tableName string) {
	writer.Write([]byte("BEGIN;\n"))
}

func (dd *DefaultDumpHelper) BeforeInsertSql(quoteSchema string, quoteTableName string) string {
	return ""
}

func (dd *DefaultDumpHelper) AfterInsert(writer io.Writer, tableName string, columns []Column) {
	writer.Write([]byte("COMMIT;\n"))
}