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76 lines
2.4 KiB
76 lines
2.4 KiB
using Connected.Expressions.Formatters;
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using Connected.Expressions.Translation;
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using Connected.Expressions.Translation.Optimization;
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using Connected.Expressions.Translation.Rewriters;
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using System.Linq.Expressions;
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namespace Connected.Expressions.Languages;
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public class Linguist
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{
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/// <summary>
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/// Construct a <see cref="Linguist"/>
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/// </summary>
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public Linguist(ExpressionCompilationContext context, QueryLanguage language, Translator translator)
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{
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Context = context;
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Language = language;
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Translator = translator;
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}
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protected ExpressionCompilationContext Context { get; }
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public QueryLanguage Language { get; }
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public Translator Translator { get; }
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/// <summary>
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/// Provides language specific query translation. Use this to apply language specific rewrites or
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/// to make assertions/validations about the query.
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/// </summary>
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public virtual Expression Translate(Expression expression)
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{
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/*
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* remove redundant layers again before cross apply rewrite
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*/
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expression = UnusedColumns.Remove(expression);
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expression = RedundantColumns.Remove(expression);
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expression = RedundantSubqueries.Remove(expression);
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/*
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* convert cross-apply and outer-apply joins into inner & left-outer-joins if possible
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*/
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var rewritten = CrossApplyRewriter.Rewrite(this.Language, expression);
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/*
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* convert cross joins into inner joins
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*/
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rewritten = CrossJoinRewriter.Rewrite(rewritten);
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if (rewritten != expression)
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{
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expression = rewritten;
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/*
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* do final reduction
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*/
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expression = UnusedColumns.Remove(expression);
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expression = RedundantSubqueries.Remove(expression);
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expression = RedundantJoins.Remove(expression);
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expression = RedundantColumns.Remove(expression);
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}
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return expression;
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}
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/// <summary>
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/// Converts the query expression into text of this query language
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/// </summary>
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public virtual string Format(Expression expression)
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{
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/*
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* use common SQL formatter by default
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*/
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return SqlFormatter.Format(expression);
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}
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/// <summary>
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/// Determine which sub-expressions must be parameters
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/// </summary>
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public virtual Expression Parameterize(Expression expression)
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{
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return Parameterizer.Parameterize(Language, expression);
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}
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} |