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SQL WHERE IN(...) does not preserve order, meaning certain playlist

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operations could result in jumbled track orders. This fixes that by
eating some extra memory temporarily.
This commit is contained in:
casey langen 2017-12-01 00:31:54 -08:00
parent 78c57b8f10
commit 5111b3ed30
1 changed files with 19 additions and 3 deletions
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22
src/core/library/LocalSimpleDataProvider.cpp
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@ -91,7 +91,7 @@ class ExternalIdListToTrackListQuery : public TrackListQueryBase {
protected:
virtual bool OnRun(musik::core::db::Connection& db) {
std::string sql = "SELECT id FROM tracks WHERE external_id IN(";
std::string sql = "SELECT id, external_id FROM tracks WHERE external_id IN(";
for (size_t i = 0; i < externalIdCount; i++) {
sql += (i == 0) ? "?" : ",?";
}
@ -103,10 +103,26 @@ class ExternalIdListToTrackListQuery : public TrackListQueryBase {
query.BindText(i, externalIds[i]);
}
this->result = std::make_shared<TrackList>(this->library);
/* gotta eat up some memory to preserve the input order. map the
external id to the id so we can ensure we return the list in the
same order it was requested. this is faster than executing one
query per ID (we do this because WHERE IN() does not preserve input
ordering... */
struct Record { int64_t id; std::string externalId; };
std::map<std::string, int64_t> records;
while (query.Step() == Row) {
result->Add(query.ColumnInt64(0));
records[query.ColumnText(1)] = query.ColumnInt64(0);
}
/* order the output here... */
this->result = std::make_shared<TrackList>(this->library);
auto end = records.end();
for (size_t i = 0; i < externalIdCount; i++) {
auto r = records.find(externalIds[i]);
if (r != end) {
this->result->Add(r->second);
}
}
return true;