CYQ.Data 支持 PostgreSQL 数据库

时间:2023-03-10 02:14:53
CYQ.Data 支持 PostgreSQL 数据库

前言:

很久之前,就有同学问我CYQ.Data能不能支持下PostgreSQL,之后小做了下调查,发现这个数据库用的人少,加上各种因素,就一直没动手。

前两天,不小心看了一下Github上的消息:

CYQ.Data 支持 PostgreSQL 数据库

看到这个问题又被重新提了出来了,于是,闹吧!

下面分享一下支持该数据库要处理的过程,让大伙明白CYQ.Data要支持一种新的数据库,需要花多少功夫。

1、找到数据库的驱动程序:Npgsql.dll

网上查找了点相关知识,发现.NET 里操作PostgreSQL有两种提供的dll,一种是正规的收费的,另一种是开源的Npgsql.dll,因此这里选择了开源的。

在Nuget上可以搜索Npgsql,不过上面的版本要求依赖的版本很高,于是我找了最早的版本开始支持,毕竟CYQ.Data 是从支持最低2.0及以上的。

这里是找到的下载低版本支持的网址:http://pgfoundry.org/frs/?group_id=1000140&release_id=1889

同时,下载的两个2.0和4.0两个版本,也一并上传到:https://github.com/cyq1162/cyqdata/tree/master/文档

2、创建PostgreDal.cs,实现动态加载DLL

CYQ.Data 支持 PostgreSQL 数据库

添加动态加载的代码:

using System;
using System.Collections.Generic;
using System.Text;
using System.Reflection;
using System.Data.Common;
using CYQ.Data.Cache;
using System.IO; namespace CYQ.Data
{
internal class PostgreDal : DbBase
{
public PostgreDal(ConnObject co)
: base(co)
{ }
internal static Assembly GetAssembly()
{
object ass = CacheManage.LocalInstance.Get("Postgre_Assembly");
if (ass == null)
{
try
{
string name = string.Empty;
if (File.Exists(AppConst.RunFolderPath + "Npgsql.dll"))
{
name = "Npgsql";
}
else
{
name = "Can't find the Npgsql.dll";
Error.Throw(name);
}
ass = Assembly.Load(name);
CacheManage.LocalInstance.Set("Postgre_Assembly", ass, );
}
catch (Exception err)
{
string errMsg = err.Message;
Error.Throw(errMsg);
}
}
return ass as Assembly;
}
protected override DbProviderFactory GetFactory(string providerName)
{
object factory = CacheManage.LocalInstance.Get("Postgre_Factory");
if (factory == null)
{
Assembly ass = GetAssembly();
factory = ass.GetType("Npgsql.NpgsqlFactory").GetField("Instance").GetValue(null);
// factory = ass.CreateInstance("Npgsql.NpgsqlFactory.Instance");
if (factory == null)
{
throw new System.Exception("Can't Create NpgsqlFactory in Npgsql.dll");
}
else
{
CacheManage.LocalInstance.Set("Postgre_Factory", factory, );
} }
return factory as DbProviderFactory; } protected override bool IsExistsDbName(string dbName)
{
try
{
IsAllowRecordSql = false;
bool result = ExeScalar("select 1 from pg_catalog.pg_database where datname='" + dbName + "'", false) != null;
IsAllowRecordSql = true;
return result;
}
catch
{
return true;
}
}
public override char Pre
{
get
{
return ':';
}
}
public override void AddReturnPara()
{ }
}
}

几点说明:

、GetFactory方法,其它dll框架提供的都是直接实例化,而Npgsql.dll提供却是单例属性,所以代码有点变化。
、Npgsql操作参数化的符号是“:”号。

3、DalCreate.cs追加PostgreSql类型及数据库链接解析

CYQ.Data 支持 PostgreSQL 数据库

这里重点发现postgresql和mssql两者的数据库链接格式都一致:

server=...;uid=xxx;pwd=xxx;database=xxx;

因此从单纯的语句上,根本无法判断从属于哪种数据库。

经过小小的思考,解决方案出来了:

else
{
//postgre和mssql的链接语句一样,这里用database=和uid=顺序来决定;database写在后面的,为postgre
int dbIndex = connString.IndexOf("database=", StringComparison.OrdinalIgnoreCase);
int uid = connString.IndexOf("uid=", StringComparison.OrdinalIgnoreCase);
if (uid > && uid < dbIndex && File.Exists(AppConfig.RunPath + "Npgsql.dll"))
{
return PostgreClient;
}
return SqlClient;
}

简的说:只有满足引用了npgsql.dll以及database写在uid之后两种条件下,判断为postgresql,其它的都回归到mssql。

4、处理表结构语句:获取数据库表以及表的结构语句:

这一块花的时间比较多,网上也费了点时间查了不少资料,最后自己写了语句:

获取数据库所有表:

internal static string GetPostgreTables(string dbName)
{
return string.Format("select table_name as TableName,cast(obj_description(relfilenode,'pg_class') as varchar) as Description from information_schema.tables t left join pg_class p on t.table_name=p.relname where table_schema='public' and table_catalog='{0}'", dbName);
}

获取某表的结构:

internal static string GetPostgreColumns()
{
return @"select
a.attname AS ColumnName,
case t.typname when 'int4' then 'int' when 'int8' then 'bigint' else t.typname end AS SqlType,
coalesce(character_maximum_length,numeric_precision,-1) as MaxSize,numeric_scale as Scale,
case a.attnotnull when 'true' then 0 else 1 end AS IsNullable,
case when position('nextval' in column_default)>0 then 1 else 0 end as IsAutoIncrement,
case when o.conname is null then 0 else 1 end as IsPrimaryKey,
d.description AS Description,
i.column_default as DefaultValue
from pg_class c
left join pg_attribute a on c.oid=a.attrelid
left join pg_description d on a.attrelid=d.objoid AND a.attnum = d.objsubid
left join pg_type t on a.atttypid = t.oid
left join information_schema.columns i on i.table_schema='public' and i.table_name=c.relname and i.column_name=a.attname
left join pg_constraint o on a.attnum = o.conkey[1] and o.contype='p'
where c.relname =:TableName
and a.attnum > 0 and a.atttypid>0
ORDER BY a.attnum";
}

5、处理关键字符号

由于PostgreSQL的大小写敏感,而且关键字加需要用双引号包含(这点和SQLite一致):

CYQ.Data 支持 PostgreSQL 数据库

这里在原有的基础上加上case即可。

6、处理差异化的SQL语句:SqlCreate.cs

A、获取插入后的自增值,这里可以借用一下自增列产生的默认值:

CYQ.Data 支持 PostgreSQL 数据库

这里用默认值,替换一下nextval序列为currval序列即可。

 else if (_action.dalHelper.dalType == DalType.PostgreSQL)
{
string key = Convert.ToString(primaryCell.Struct.DefaultValue);
if (!string.IsNullOrEmpty(key))
{
key = key.Replace("nextval", "currval");
sql = sql + "; select " + key + " as OutPutValue";
}
}

B、需要引用关键字的地方:

略。。。。

7、处理分页语句:SqlCreateForPager.cs

这里PostgreSQL和分页和sqlite及mysql是一致的,因此只要在相关的地方补上case即可:

public static string GetSql(DalType dalType, string version, int pageIndex, int pageSize, object objWhere, string tableName, int rowCount, string columns, string primaryKey, bool primaryKeyIsIdentity)
{
if (string.IsNullOrEmpty(columns))
{
columns = "*";
}
pageIndex = pageIndex == ? : pageIndex;
string where = SqlFormat.GetIFieldSql(objWhere);
if (string.IsNullOrEmpty(where))
{
where = "1=1";
}
if (pageSize == )
{
return string.Format(top1Pager, columns, tableName, where);
}
if (rowCount > )//分页查询。
{
where = SqlCreate.AddOrderBy(where, primaryKey);
}
int topN = pageIndex * pageSize;//Top N 最大数
int max = (pageIndex - ) * pageSize;
int rowStart = (pageIndex - ) * pageSize + ;
int rowEnd = rowStart + pageSize - ;
string orderBy = string.Empty;
if (pageIndex == && dalType != DalType.Oracle)//第一页(oracle时 rownum 在排序条件为非数字时,和row_number()的不一样,会导致结果差异,所以分页统一用row_number()。)
{
switch (dalType)
{
case DalType.Access:
case DalType.MsSql:
case DalType.Sybase:
return string.Format(top1Pager, "top " + pageSize + " " + columns, tableName, where);
//case DalType.Oracle:
// return string.Format(top1Pager, columns, tableName, "rownum<=" + pageSize + " and " + where);
case DalType.SQLite:
case DalType.MySql:
case DalType.PostgreSQL:
return string.Format(top1Pager, columns, tableName, where + " limit " + pageSize);
}
}
else
{ switch (dalType)
{
case DalType.Access:
case DalType.MsSql:
case DalType.Sybase:
int leftNum = rowCount % pageSize;
int pageCount = leftNum == ? rowCount / pageSize : rowCount / pageSize + ;//页数
if (pageIndex == pageCount && dalType != DalType.Sybase) // 最后一页Sybase 不支持双Top order by
{
return string.Format(top2Pager, pageSize+" "+columns, "top " + (leftNum == ? pageSize : leftNum) + " * ", tableName, ReverseOrderBy(where, primaryKey), GetOrderBy(where, false, primaryKey));//反序
}
if ((pageCount > || rowCount > ) && pageIndex > pageCount / ) // 页数过后半段,反转查询
{
orderBy = GetOrderBy(where, false, primaryKey);
where = ReverseOrderBy(where, primaryKey);//事先反转一次。
topN = rowCount - max;//取后面的
int rowStartTemp = rowCount - rowEnd;
rowEnd = rowCount - rowStart;
rowStart = rowStartTemp;
}
break; }
} switch (dalType)
{
case DalType.MsSql:
case DalType.Oracle:
if (version.StartsWith(""))
{
goto temtable;
// goto top3;//sql 2000
}
int index = tableName.LastIndexOf(')');
if (index > )
{
tableName = tableName.Substring(, index + );
}
string v = dalType == DalType.Oracle ? "" : " v";
string onlyWhere = "where " + SqlCreate.RemoveOrderBy(where);
onlyWhere = SqlFormat.RemoveWhereOneEqualsOne(onlyWhere);
return string.Format(rowNumberPager, GetOrderBy(where, false, primaryKey), (columns == "*" ? "t.*" : columns), tableName, onlyWhere, v, rowStart, rowEnd);
case DalType.Sybase:
temtable:
if (primaryKeyIsIdentity)
{
bool isOk = columns == "*";
if (!isOk)
{
string kv = SqlFormat.NotKeyword(primaryKey);
string[] items = columns.Split(',');
foreach (string item in items)
{
if (string.Compare(SqlFormat.NotKeyword(item), kv, StringComparison.OrdinalIgnoreCase) == )
{
isOk = true;
break;
}
}
}
else
{
columns = "t.*";
index = tableName.LastIndexOf(')');
if (index > )
{
tableName = tableName.Substring(, index + );
}
tableName += " t ";
}
if (isOk)
{ return string.Format(tempTablePagerWithIdentity, DateTime.Now.Millisecond, topN, primaryKey, tableName, where, pageSize, columns, rowStart, rowEnd, orderBy);
}
}
return string.Format(tempTablePager, DateTime.Now.Millisecond, pageIndex * pageSize + " " + columns, tableName, where, pageSize, rowStart, rowEnd, orderBy);
case DalType.Access:
top3:
if (!string.IsNullOrEmpty(orderBy)) // 反转查询
{
return string.Format(top4Pager,columns, (rowCount - max > pageSize ? pageSize : rowCount - max), topN, tableName, where, GetOrderBy(where, true, primaryKey), GetOrderBy(where, false, primaryKey), orderBy);
}
return string.Format(top3Pager, (rowCount - max > pageSize ? pageSize : rowCount - max),columns, topN, tableName, where, GetOrderBy(where, true, primaryKey), GetOrderBy(where, false, primaryKey));
case DalType.SQLite:
case DalType.MySql:
case DalType.PostgreSQL:
if (max > && primaryKeyIsIdentity && Convert.ToString(objWhere) == "" && !tableName.Contains(" "))//单表大数量时的优化成主键访问。
{
where = string.Format("{0}>=(select {0} from {1} limit {2}, 1) limit {3}", primaryKey, tableName, max, pageSize);
return string.Format(top1Pager, columns, tableName, where);
}
return string.Format(top1Pager, columns, tableName, where + " limit " + pageSize + " offset " + max);
}
return (string)Error.Throw("Pager::No Be Support:" + dalType.ToString());
}

总结:

一个数据库的基本支持、写到这里就完成了增删改查及分页。

当然,对于CYQ.Data而言,还差一些未处理:

1、多种数据库转换互通处理:DataType.cs。

2、对表的创建修改操作:SqlCreateForSchema.cs。

3、支持多数据库兼容性写法:SqlCompatible.cs。

4、其它细节。