89 lines
3.5 KiB
C#
89 lines
3.5 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Text;
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using System.Data.Linq;
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namespace System.Data.Linq.SqlClient {
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/// <summary>
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/// After retyping and conversions take place, some functions need to be changed into more suitable calls.
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/// Example: LEN -> DATALENGTH for long text types.
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/// </summary>
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internal class SqlMethodTransformer : SqlVisitor {
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protected SqlFactory sql;
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internal SqlMethodTransformer(SqlFactory sql) {
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this.sql = sql;
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}
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internal override SqlExpression VisitFunctionCall(SqlFunctionCall fc) {
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// process the arguments
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SqlExpression result = base.VisitFunctionCall(fc);
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if (result is SqlFunctionCall) {
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SqlFunctionCall resultFunctionCall = (SqlFunctionCall)result;
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if (resultFunctionCall.Name == "LEN") {
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SqlExpression expr = resultFunctionCall.Arguments[0];
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if (expr.SqlType.IsLargeType && !expr.SqlType.SupportsLength) {
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result = sql.DATALENGTH(expr);
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if (expr.SqlType.IsUnicodeType) {
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result = sql.ConvertToInt(sql.Divide(result, sql.ValueFromObject(2, expr.SourceExpression)));
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}
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}
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}
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// If the return type of the sql function is not compatible with
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// the expected CLR type of the function, inject a conversion. This
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// step must be performed AFTER SqlRetyper has run.
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Type clrType = resultFunctionCall.SqlType.GetClosestRuntimeType();
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bool skipConversion = SqlMethodTransformer.SkipConversionForDateAdd(resultFunctionCall.Name,
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resultFunctionCall.ClrType,
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clrType);
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if ((resultFunctionCall.ClrType != clrType) && !skipConversion) {
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result = sql.ConvertTo(resultFunctionCall.ClrType, resultFunctionCall);
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}
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}
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return result;
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}
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internal override SqlExpression VisitUnaryOperator(SqlUnary fc) {
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// process the arguments
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SqlExpression result = base.VisitUnaryOperator(fc);
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if (result is SqlUnary) {
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SqlUnary unary = (SqlUnary)result;
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switch (unary.NodeType) {
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case SqlNodeType.ClrLength:
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SqlExpression expr = unary.Operand;
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result = sql.DATALENGTH(expr);
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if (expr.SqlType.IsUnicodeType) {
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result = sql.Divide(result, sql.ValueFromObject(2, expr.SourceExpression));
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}
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result = sql.ConvertToInt(result);
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break;
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default:
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break;
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}
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}
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return result;
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}
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// We don't inject a conversion for DATEADD if doing so will downgrade the result to
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// a less precise type.
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//
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private static bool SkipConversionForDateAdd(string functionName, Type expected, Type actual) {
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if (string.Compare(functionName, "DATEADD", StringComparison.OrdinalIgnoreCase) != 0)
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return false;
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return (expected == typeof(DateTime) && actual == typeof(DateTimeOffset));
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}
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}
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}
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