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7fc901d1b3
Ordering is done by replacing the straight Vector holding the query result in the SQLResult object with a dedicated Vector subclass that inserts result rows according to their sort key using a binary search. This is done in the ResultSet class. There are limitations: - "SELECT ... ORDER BY 1" (or 2 or 3 etc) is supposed to sort by the n-th result column. This doesn't work yet - "SELECT ... column-expression alias ... ORDER BY alias" is supposed to sort by the column with the given alias. This doesn't work yet What does work however is something like ```SELECT foo FROM bar SORT BY quux``` i.e. sorted by a column not in the result set. Once functions are supported it should be possible to sort by random functions.
38 lines
909 B
C++
38 lines
909 B
C++
/*
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* Copyright (c) 2022, Jan de Visser <jan@de-visser.net>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <LibSQL/ResultSet.h>
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namespace SQL {
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size_t ResultSet::binary_search(Tuple const& sort_key, size_t low, size_t high)
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{
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if (high <= low) {
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auto compare = sort_key.compare(at(low).sort_key);
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return (compare > 0) ? low + 1 : low;
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}
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auto mid = (low + high) / 2;
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auto compare = sort_key.compare(at(mid).sort_key);
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if (compare == 0)
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return mid + 1;
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if (compare > 0)
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return binary_search(sort_key, mid + 1, high);
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return binary_search(sort_key, low, mid);
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}
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void ResultSet::insert_row(Tuple const& row, Tuple const& sort_key)
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{
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if ((sort_key.size() == 0) || is_empty()) {
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empend(row, sort_key);
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return;
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}
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auto ix = binary_search(sort_key, 0, size() - 1);
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insert(ix, ResultRow { row, sort_key });
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}
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}
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