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50 lines
1.4 KiB
C++
50 lines
1.4 KiB
C++
#pragma once
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#include <DB/Core/Block.h>
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#include <DB/Storages/ColumnDefault.h>
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#include <DB/Interpreters/ExpressionAnalyzer.h>
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#include <utility>
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namespace DB
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{
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inline void evaluateMissingDefaults(Block & block,
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const NamesAndTypesList & required_columns,
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const ColumnDefaults & column_defaults,
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const Context & context)
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{
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if (column_defaults.empty())
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return;
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ASTPtr default_expr_list{std::make_unique<ASTExpressionList>().release()};
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for (const auto & column : required_columns)
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{
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if (block.has(column.name))
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continue;
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const auto it = column_defaults.find(column.name);
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/// expressions must be cloned to prevent modification by the ExpressionAnalyzer
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if (it != column_defaults.end())
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default_expr_list->children.emplace_back(
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setAlias(it->second.expression->clone(), it->first));
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}
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/// nothing to evaluate
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if (default_expr_list->children.empty())
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return;
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/** ExpressionAnalyzer eliminates "unused" columns, in order to ensure their safety
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* we are going to operate on a copy instead of the original block */
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Block copy_block{block};
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/// evaluate default values for defaulted columns
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ExpressionAnalyzer{default_expr_list, context, required_columns}.getActions(true)->execute(copy_block);
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/// move evaluated columns to the original block
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for (auto & column_name_type : copy_block.getColumns())
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block.insert(std::move(column_name_type));
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}
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}
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