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80 lines
2.2 KiB
C++
80 lines
2.2 KiB
C++
#pragma once
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#include <string>
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#include <Columns/IColumn.h>
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namespace DB
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{
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struct DictionaryStructure;
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class WriteBuffer;
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/** Builds a query to load data from external database.
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*/
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struct ExternalQueryBuilder
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{
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const DictionaryStructure & dict_struct;
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const std::string & db;
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const std::string & table;
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const std::string & where;
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/// Method to quote identifiers.
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/// NOTE There could be differences in escaping rules inside quotes. Escaping rules may not match that required by specific external DBMS.
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enum QuotingStyle
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{
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None, /// Write as-is, without quotes.
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Backticks, /// `mysql` style
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DoubleQuotes /// "postgres" style
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};
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QuotingStyle quoting_style;
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ExternalQueryBuilder(
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const DictionaryStructure & dict_struct,
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const std::string & db,
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const std::string & table,
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const std::string & where,
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QuotingStyle quoting_style);
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/** Generate a query to load all data. */
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std::string composeLoadAllQuery() const;
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/** Generate a query to load data by set of UInt64 keys. */
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std::string composeLoadIdsQuery(const std::vector<UInt64> & ids);
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/** Generate a query to load data by set of composite keys.
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* There are two methods of specification of composite keys in WHERE:
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* 1. (x = c11 AND y = c12) OR (x = c21 AND y = c22) ...
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* 2. (x, y) IN ((c11, c12), (c21, c22), ...)
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*/
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enum LoadKeysMethod
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{
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AND_OR_CHAIN,
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IN_WITH_TUPLES,
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};
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std::string composeLoadKeysQuery(
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const Columns & key_columns,
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const std::vector<size_t> & requested_rows,
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LoadKeysMethod method);
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private:
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/// Expression in form (x = c1 AND y = c2 ...)
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void composeKeyCondition(const Columns & key_columns, const size_t row, WriteBuffer & out) const;
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/// Expression in form (x, y, ...)
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std::string composeKeyTupleDefinition() const;
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/// Expression in form (c1, c2, ...)
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void composeKeyTuple(const Columns & key_columns, const size_t row, WriteBuffer & out) const;
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/// Write string with specified quoting style.
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void writeQuoted(const std::string & s, WriteBuffer & out) const;
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};
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}
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