ClickHouse/src/Storages/IndicesDescription.h

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#pragma once
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#include <Core/Types.h>
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#include <memory>
#include <vector>
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#include <Core/Field.h>
#include <Interpreters/ExpressionActions.h>
#include <Parsers/IAST_fwd.h>
#include <Storages/ColumnsDescription.h>
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namespace DB
{
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/// Description of non-primary index for Storage
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struct IndexDescription
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{
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/// Definition AST of index
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ASTPtr definition_ast;
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/// List of expressions for index calculation
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ASTPtr expression_list_ast;
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/// Index name
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String name;
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/// Index type (minmax, set, bloom filter, etc.)
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String type;
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/// Prepared expressions for index calculations
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ExpressionActionsPtr expression;
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/// Index arguments, for example probability for bloom filter
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FieldVector arguments;
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/// Names of index columns (not to be confused with required columns)
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Names column_names;
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/// Data types of index columns
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DataTypes data_types;
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/// Sample block with index columns. (NOTE: columns in block are empty, but not nullptr)
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Block sample_block;
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/// Index granularity, make sense for skip indices
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size_t granularity;
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/// Parse index from definition AST
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static IndexDescription getIndexFromAST(const ASTPtr & definition_ast, const ColumnsDescription & columns, const Context & context);
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IndexDescription() = default;
/// We need custom copy constructors because we don't want
/// unintentionaly share AST variables and modify them.
IndexDescription(const IndexDescription & other);
IndexDescription & operator=(const IndexDescription & other);
/// Recalculate index with new columns because index expression may change
/// if something change in columns.
void recalculateWithNewColumns(const ColumnsDescription & new_columns, const Context & context);
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};
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/// All secondary indices in storage
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struct IndicesDescription : public std::vector<IndexDescription>
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{
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/// Index with name exists
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bool has(const String & name) const;
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/// Convert description to string
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String toString() const;
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/// Parse description from string
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static IndicesDescription parse(const String & str, const ColumnsDescription & columns, const Context & context);
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/// Return common expression for all stored indices
ExpressionActionsPtr getSingleExpressionForIndices(const ColumnsDescription & columns, const Context & context) const;
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};
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}