io.questdb.cairo.sql.DataFrameCursor Maven / Gradle / Ivy
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*
* Copyright (c) 2014-2019 Appsicle
* Copyright (c) 2019-2023 QuestDB
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
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package io.questdb.cairo.sql;
import io.questdb.cairo.TableReader;
import org.jetbrains.annotations.Nullable;
import org.jetbrains.annotations.TestOnly;
import java.io.Closeable;
/**
* A cursor for managing position of operations within data frames
*
* Interfaces which extend Closeable are not optionally-closeable.
* close() method must be called after other calls are complete.
*/
public interface DataFrameCursor extends Closeable, SymbolTableSource {
default void calculateSize(RecordCursor.Counter counter) {
}
/**
* Must be closed after other calls are complete
*/
@Override
void close();
StaticSymbolTable getSymbolTable(int columnIndex);
// same TableReader is available on each data frame
TableReader getTableReader();
StaticSymbolTable newSymbolTable(int columnIndex);
/**
* @return the next element in the data frame
* @throws io.questdb.cairo.DataUnavailableException when the queried partition is in cold storage
*/
@Nullable DataFrame next();
/**
* Reload the data frame and return the cursor to the beginning of
* the data frame
*
* @return true when reload data has changed, false otherwise
*/
@TestOnly
boolean reload();
/**
* @return number of items in the data frame
*/
long size();
/**
* Positions data frame at the given row number.
*
* @param rowsToSkip number of rows to skip in table. Rows are numbered 0...row_count-1
* @return data frame and position (lo) of given rowsToSkip (according to cursor order).
* @throws io.questdb.cairo.DataUnavailableException when the queried partition is in cold storage
*/
default @Nullable DataFrame skipTo(RecordCursor.Counter rowsToSkip) {
throw new UnsupportedOperationException();
}
/**
* @return true if cursor supports random record access (without having to iterate through all results).
*/
default boolean supportsRandomAccess() {
return false;
}
/**
* Return the cursor to the beginning of the data frame
*/
void toTop();
}