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69 lines
2.5 KiB
C++
69 lines
2.5 KiB
C++
#pragma once
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#include <Core/Block.h>
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#include <Processors/Formats/IRowInputFormat.h>
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#include <Formats/FormatSettings.h>
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#include <Common/HashTable/HashMap.h>
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namespace DB
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{
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class ReadBuffer;
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/** A stream for reading data in JSON format, where each row is represented by a separate JSON object.
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* Objects can be separated by feed return, other whitespace characters in any number and possibly a comma.
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* Fields can be listed in any order (including, in different lines there may be different order),
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* and some fields may be missing.
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*/
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class JSONEachRowRowInputFormat : public IRowInputFormat
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{
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public:
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JSONEachRowRowInputFormat(ReadBuffer & in_, const Block & header, Params params, const FormatSettings & format_settings);
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String getName() const override { return "JSONEachRowRowInputFormat"; }
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bool readRow(MutableColumns & columns, RowReadExtension & ext) override;
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bool allowSyncAfterError() const override { return true; }
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void syncAfterError() override;
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private:
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const String & columnName(size_t i) const;
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size_t columnIndex(const StringRef & name, size_t key_index);
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bool advanceToNextKey(size_t key_index);
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void skipUnknownField(const StringRef & name_ref);
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StringRef readColumnName(ReadBuffer & buf);
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void readField(size_t index, MutableColumns & columns);
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void readJSONObject(MutableColumns & columns);
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void readNestedData(const String & name, MutableColumns & columns);
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private:
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const FormatSettings format_settings;
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/// Buffer for the read from the stream field name. Used when you have to copy it.
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/// Also, if processing of Nested data is in progress, it holds the common prefix
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/// of the nested column names (so that appending the field name to it produces
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/// the full column name)
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String current_column_name;
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/// If processing Nested data, holds the length of the common prefix
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/// of the names of related nested columns. For example, for a table
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/// created as follows
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/// CREATE TABLE t (n Nested (i Int32, s String))
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/// the nested column names are 'n.i' and 'n.s' and the nested prefix is 'n.'
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size_t nested_prefix_length = 0;
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std::vector<UInt8> read_columns;
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/// Hash table match `field name -> position in the block`. NOTE You can use perfect hash map.
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using NameMap = HashMap<StringRef, size_t, StringRefHash>;
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NameMap name_map;
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/// Cached search results for previous row (keyed as index in JSON object) - used as a hint.
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std::vector<NameMap::iterator> prev_positions;
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};
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}
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