ClickHouse/dbms/src/Interpreters/ExternalTablesVisitor.h

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#pragma once
#include <Interpreters/Context.h>
#include <Parsers/IAST.h>
#include <Parsers/ASTIdentifier.h>
#include <Common/typeid_cast.h>
#include <Interpreters/InDepthNodeVisitor.h>
#include <Interpreters/IdentifierSemantic.h>
namespace DB
{
/// If node is ASTIdentifier try to extract external_storage.
class ExternalTablesMatcher
{
public:
struct Data
{
const Context & context;
Tables & external_tables;
};
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static void visit(ASTPtr & ast, Data & data)
{
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if (const auto * t = ast->as<ASTIdentifier>())
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visit(*t, ast, data);
}
static bool needChildVisit(ASTPtr &, const ASTPtr &) { return true; }
private:
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static void visit(const ASTIdentifier & node, ASTPtr &, Data & data)
{
if (auto opt_name = IdentifierSemantic::getTableName(node))
if (StoragePtr external_storage = data.context.tryGetExternalTable(*opt_name))
data.external_tables[*opt_name] = external_storage;
}
};
/// Finds in the query the usage of external tables. Fills in external_tables.
using ExternalTablesVisitor = InDepthNodeVisitor<ExternalTablesMatcher, false>;
}