124 lines
3.7 KiB
C#
124 lines
3.7 KiB
C#
using System.Text;
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namespace Marr.Data.QGen
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{
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public class RowCountQueryDecorator : IQuery
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{
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private SelectQuery _innerQuery;
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public RowCountQueryDecorator(SelectQuery innerQuery)
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{
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_innerQuery = innerQuery;
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}
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public string Generate()
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{
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// Decide which type of paging query to create
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if (_innerQuery.IsView || _innerQuery.IsJoin)
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{
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return ComplexRowCount();
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}
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else
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{
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return SimpleRowCount();
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}
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}
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/// <summary>
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/// Generates a row count query for a multiple table joined query (groups by the parent entity).
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/// </summary>
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/// <returns></returns>
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private string ComplexRowCount()
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{
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// Create paged query
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StringBuilder sql = new StringBuilder();
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sql.AppendLine("WITH GroupCTE AS (");
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sql.Append("SELECT ").AppendLine(BuildBaseTablePKColumns());
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BuildGroupColumn(sql);
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_innerQuery.BuildFromClause(sql);
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_innerQuery.BuildJoinClauses(sql);
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_innerQuery.BuildWhereClause(sql);
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sql.AppendLine(")");
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BuildSelectCountClause(sql);
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sql.AppendLine("FROM GroupCTE");
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sql.AppendLine("WHERE GroupRow = 1");
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return sql.ToString();
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}
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/// <summary>
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/// Generates a row count query for a single table query (no joins).
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/// </summary>
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/// <returns></returns>
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private string SimpleRowCount()
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{
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StringBuilder sql = new StringBuilder();
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BuildSelectCountClause(sql);
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_innerQuery.BuildFromClause(sql);
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_innerQuery.BuildJoinClauses(sql);
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_innerQuery.BuildWhereClause(sql);
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return sql.ToString();
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}
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private void BuildGroupColumn(StringBuilder sql)
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{
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string baseTablePKColumns = BuildBaseTablePKColumns();
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sql.AppendFormat(", ROW_NUMBER() OVER (PARTITION BY {0} ORDER BY {1}) As GroupRow ", baseTablePKColumns, baseTablePKColumns);
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}
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private string BuildBaseTablePKColumns()
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{
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Table baseTable = GetBaseTable();
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StringBuilder sb = new StringBuilder();
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foreach (var col in baseTable.Columns.PrimaryKeys)
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{
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if (sb.Length > 0)
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sb.AppendLine(", ");
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string colName = _innerQuery.IsView ?
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_innerQuery.NameOrAltName(col.ColumnInfo) :
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col.ColumnInfo.Name;
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sb.AppendFormat(_innerQuery.Dialect.CreateToken(string.Concat(baseTable.Alias, ".", colName)));
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}
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return sb.ToString();
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}
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private void BuildSelectCountClause(StringBuilder sql)
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{
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sql.AppendLine("SELECT COUNT(*)");
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}
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private Table GetBaseTable()
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{
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Table baseTable = null;
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if (_innerQuery.Tables[0] is View)
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{
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baseTable = (_innerQuery.Tables[0] as View).Tables[0];
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}
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else
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{
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baseTable = _innerQuery.Tables[0];
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}
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return baseTable;
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}
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}
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}
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/*
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WITH GroupCTE AS
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(
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SELECT [t0].[ID],[t0].[OrderName],[t1].[ID] AS OrderItemID,[t1].[OrderID],[t1].[ItemDescription],[t1].[Price],
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ROW_NUMBER() OVER (PARTITION BY [t0].[ID] ORDER BY [t0].[OrderName]) As GroupRow
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FROM [Order] [t0]
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LEFT JOIN [OrderItem] [t1] ON (([t0].[ID] = [t1].[OrderID]))
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--WHERE (([t0].[OrderName] = @P0))
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)
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SELECT * FROM GroupCTE
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WHERE GroupRow = 1
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*/ |