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141 lines (117 loc) · 4.5 KB
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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace DapperExtensions.Sql
{
public class SqlServerDialect : SqlDialectBase
{
public override char OpenQuote
{
get { return '['; }
}
public override char CloseQuote
{
get { return ']'; }
}
public override string GetIdentitySql(string tableName)
{
return string.Format("SELECT CAST(SCOPE_IDENTITY() AS BIGINT) AS [Id]");
}
public override string GetPagingSql(string sql, int page, int resultsPerPage, IDictionary<string, object> parameters)
{
if (string.IsNullOrEmpty(sql))
{
throw new ArgumentNullException("SQL");
}
if (parameters == null)
{
throw new ArgumentNullException("Parameters");
}
int selectIndex = GetSelectEnd(sql) + 1;
string orderByClause = GetOrderByClause(sql);
if (orderByClause == null)
{
orderByClause = "ORDER BY CURRENT_TIMESTAMP";
}
string projectedColumns = GetColumnNames(sql).Aggregate(new StringBuilder(), (sb, s) => (sb.Length == 0 ? sb : sb.Append(", ")).Append(GetColumnName("_proj", s, null)), sb => sb.ToString());
string newSql = sql
.Replace(" " + orderByClause, string.Empty)
.Insert(selectIndex, string.Format("ROW_NUMBER() OVER(ORDER BY {0}) AS {1}, ", orderByClause.Substring(9), GetColumnName(null, "_row_number", null)));
string result = string.Format("SELECT TOP({0}) {1} FROM ({2}) [_proj] WHERE {3} >= @_pageStartRow ORDER BY {3}",
resultsPerPage, projectedColumns.Trim(), newSql, GetColumnName("_proj", "_row_number", null));
int startValue = (page * resultsPerPage) + 1;
parameters.Add("@_pageStartRow", startValue);
return result;
}
protected string GetOrderByClause(string sql)
{
int orderByIndex = sql.LastIndexOf(" ORDER BY ", StringComparison.InvariantCultureIgnoreCase);
if (orderByIndex == -1)
{
return null;
}
string result = sql.Substring(orderByIndex).Trim();
int whereIndex = result.IndexOf(" WHERE ", StringComparison.InvariantCultureIgnoreCase);
if (whereIndex == -1)
{
return result;
}
return result.Substring(0, whereIndex).Trim();
}
protected int GetFromStart(string sql)
{
int selectCount = 0;
string[] words = sql.Split(' ');
int fromIndex = 0;
foreach (var word in words)
{
if (word.Equals("SELECT", StringComparison.InvariantCultureIgnoreCase))
{
selectCount++;
}
if (word.Equals("FROM", StringComparison.InvariantCultureIgnoreCase))
{
selectCount--;
if (selectCount == 0)
{
break;
}
}
fromIndex += word.Length + 1;
}
return fromIndex;
}
protected virtual int GetSelectEnd(string sql)
{
if (sql.StartsWith("SELECT DISTINCT", StringComparison.InvariantCultureIgnoreCase))
{
return 15;
}
if (sql.StartsWith("SELECT", StringComparison.InvariantCultureIgnoreCase))
{
return 6;
}
throw new ArgumentException("SQL must be a SELECT statement.", "sql");
}
protected virtual IList<string> GetColumnNames(string sql)
{
int start = GetSelectEnd(sql);
int stop = GetFromStart(sql);
string[] columnSql = sql.Substring(start, stop - start).Split(',');
List<string> result = new List<string>();
foreach (string c in columnSql)
{
int index = c.IndexOf(" AS ", StringComparison.InvariantCultureIgnoreCase);
if (index > 0)
{
result.Add(c.Substring(index + 4).Trim());
continue;
}
string[] colParts = c.Split('.');
result.Add(colParts[colParts.Length - 1].Trim());
}
return result;
}
}
}