91 lines
4.3 KiB
C#
91 lines
4.3 KiB
C#
using System.Data.Linq.Mapping;
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namespace System.Data.Linq.SqlClient {
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/// <summary>
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/// Locate cases in which there is a 'Bit' but a 'Predicate' is expected or vice-versa.
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/// Transform these expressions into expressions of the expected type.
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/// </summary>
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internal class SqlBooleanizer {
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private class Booleanizer : SqlBooleanMismatchVisitor {
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private SqlFactory sql;
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internal Booleanizer(TypeSystemProvider typeProvider, MetaModel model) {
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this.sql = new SqlFactory(typeProvider, model);
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}
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internal override SqlSelect VisitSelect(SqlSelect select) {
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// DevDiv 179191
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if (select.Where != null && select.Where.NodeType == SqlNodeType.Coalesce) {
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SqlBinary bin = (SqlBinary)select.Where;
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if (bin.Right.NodeType == SqlNodeType.Value) {
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SqlValue value = (SqlValue)bin.Right;
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if (value.Value != null && value.Value.GetType() == typeof(bool) && (bool)value.Value == false) {
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select.Where = bin.Left;
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}
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}
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}
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return base.VisitSelect(select);
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}
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internal override SqlExpression ConvertValueToPredicate(SqlExpression valueExpression) {
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// Transform the 'Bit' expression into a 'Predicate' by forming the
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// following operation:
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// OriginalExpr = 1
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// Yukon and later could also handle:
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// OriginalExpr = 'true'
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// but Sql2000 does not support this.
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return new SqlBinary(SqlNodeType.EQ,
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valueExpression.ClrType, sql.TypeProvider.From(typeof(bool)),
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valueExpression,
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sql.Value(typeof(bool), valueExpression.SqlType, true, false, valueExpression.SourceExpression)
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);
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}
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internal override SqlExpression ConvertPredicateToValue(SqlExpression predicateExpression) {
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// Transform the 'Predicate' expression into a 'Bit' by forming the
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// following operation:
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// CASE
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// WHEN predicateExpression THEN 1
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// ELSE NOT(predicateExpression) THEN 0
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// ELSE NULL
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// END
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// Possible simplification to the generated SQL would be to detect when 'predicateExpression'
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// is SqlUnary(NOT) and use its operand with the literal 1 and 0 below swapped.
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SqlExpression valueTrue = sql.ValueFromObject(true, false, predicateExpression.SourceExpression);
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SqlExpression valueFalse = sql.ValueFromObject(false, false, predicateExpression.SourceExpression);
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if (SqlExpressionNullability.CanBeNull(predicateExpression) != false) {
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SqlExpression valueNull = sql.Value(valueTrue.ClrType, valueTrue.SqlType, null, false, predicateExpression.SourceExpression);
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return new SqlSearchedCase(
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predicateExpression.ClrType,
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new SqlWhen[] {
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new SqlWhen(predicateExpression, valueTrue),
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new SqlWhen(new SqlUnary(SqlNodeType.Not, predicateExpression.ClrType, predicateExpression.SqlType, predicateExpression, predicateExpression.SourceExpression), valueFalse)
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},
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valueNull,
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predicateExpression.SourceExpression
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);
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}
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else {
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return new SqlSearchedCase(
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predicateExpression.ClrType,
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new SqlWhen[] { new SqlWhen(predicateExpression, valueTrue) },
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valueFalse,
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predicateExpression.SourceExpression
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);
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}
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}
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}
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/// <summary>
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/// Rationalize boolean expressions for the given node.
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/// </summary>
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internal static SqlNode Rationalize(SqlNode node, TypeSystemProvider typeProvider, MetaModel model) {
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return new Booleanizer(typeProvider, model).Visit(node);
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}
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}
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}
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