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48 lines
1.1 KiB
C++
48 lines
1.1 KiB
C++
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#pragma once
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namespace DB
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{
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/// Finds in the query the usage of external tables (as table identifiers). Fills in external_tables.
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class ExternalTablesVisitor
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{
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public:
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ExternalTablesVisitor(const Context & context_, Tables & tables)
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: context(context_),
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external_tables(tables)
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{}
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void visit(ASTPtr & ast) const
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{
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/// Traverse from the bottom. Intentionally go into subqueries.
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for (auto & child : ast->children)
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visit(child);
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tryVisit<ASTIdentifier>(ast);
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}
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private:
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const Context & context;
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Tables & external_tables;
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void visit(const ASTIdentifier * node, ASTPtr &) const
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{
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if (node->special())
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if (StoragePtr external_storage = context.tryGetExternalTable(node->name))
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external_tables[node->name] = external_storage;
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}
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template <typename T>
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bool tryVisit(ASTPtr & ast) const
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{
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if (const T * t = typeid_cast<const T *>(ast.get()))
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{
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visit(t, ast);
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return true;
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}
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return false;
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}
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};
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}
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