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90 lines
3.2 KiB
C++
90 lines
3.2 KiB
C++
#pragma once
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#include <Core/Names.h>
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#include <Interpreters/InDepthNodeVisitor.h>
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#include <Storages/ColumnsDescription.h>
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namespace DB
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{
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class IAST;
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using ASTPtr = std::shared_ptr<IAST>;
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class IDataType;
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class ASTFunction;
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class ASTIdentifier;
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using DataTypePtr = std::shared_ptr<const IDataType>;
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/// Visits AST node to rewrite alias columns in query
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/// Currently works only 3 kind ways below
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/// For example:
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// CREATE TABLE test_table
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// (
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// `timestamp` DateTime,
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// `value` UInt64,
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// `day` Date ALIAS toDate(timestamp),
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// `day1` Date ALIAS day + 1,
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// `day2` Date ALIAS day1 + 1,
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// `time` DateTime ALIAS timestamp
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// )ENGINE = MergeTree
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// PARTITION BY toYYYYMMDD(timestamp)
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// ORDER BY timestamp SETTINGS index_granularity = 1;
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/// 1. Rewrite the filters in query when enable optimize_respect_aliases
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/// this could help with `optimize_trivial_count`, Partition Prune in `KeyCondition` and secondary indexes.
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/// eg: select max(value) from test_table where day2 = today(), filters will be: ((toDate(timestamp) + 1) + 1) = today() .
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/// 2. Alias on alias for `required_columns` extracted in `InterpreterSelectQuery.cpp`, it could help get all dependent physical columns for query.
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/// eg: select day2 from test_table. `required_columns` can got require columns from the temporary rewritten AST `((toDate(timestamp) + 1) + 1)`.
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/// 3. Help with `optimize_aggregation_in_order` and `optimize_read_in_order` in `ReadInOrderOptimizer.cpp`:
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/// For queries with alias columns in `orderBy` and `groupBy`, these ASTs will not change.
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/// But we generate temporary asts and generate temporary Actions to get the `InputOrderInfo`
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/// eg: select day1 from test_table order by day1;
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class ColumnAliasesMatcher
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{
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public:
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using Visitor = InDepthNodeVisitor<ColumnAliasesMatcher, false, true>;
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struct Data
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{
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const ColumnsDescription & columns;
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/// columns from array_join_result_to_source cannot be expanded.
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NameSet array_join_result_columns;
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NameSet array_join_source_columns;
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ContextPtr context;
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const std::unordered_set<IAST *> & excluded_nodes;
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/// private_aliases are from lambda, so these are local names.
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NameSet private_aliases;
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/// Check if query is changed by this visitor.
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bool changed = false;
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Data(const ColumnsDescription & columns_, const NameToNameMap & array_join_result_columns_, ContextPtr context_, const std::unordered_set<IAST *> & excluded_nodes_)
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: columns(columns_), context(context_), excluded_nodes(excluded_nodes_)
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{
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for (const auto & [result, source] : array_join_result_columns_)
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{
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array_join_result_columns.insert(result);
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array_join_source_columns.insert(source);
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}
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}
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};
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static void visit(ASTPtr & ast, Data & data);
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static bool needChildVisit(const ASTPtr & node, const ASTPtr & child, const Data & data);
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private:
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static void visit(ASTIdentifier & node, ASTPtr & ast, Data & data);
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static void visit(ASTFunction & node, ASTPtr & ast, Data & data);
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};
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using ColumnAliasesVisitor = ColumnAliasesMatcher::Visitor;
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}
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