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Speed up the REGEXP implementation by adding a cache

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Speed up the new REGEXP implementation based on QRegularExpression for
SQL queries by adding a cache for compiled regular expression objects.

See issue #2052.
This commit is contained in:
Martin Kleusberg
2019-11-22 12:16:53 +01:00
parent 74a16912e1
commit 317918d7cd
1 changed files with 28 additions and 5 deletions
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33
src/sqlitedb.cpp
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@@ -128,15 +128,38 @@ void DBBrowserDB::errorLogCallback(void* /*user_data*/, int error_code, const ch
static void regexp(sqlite3_context* ctx, int /*argc*/, sqlite3_value* argv[])
{
// This is a cache for the last 50 regular expressions. Compiling them takes some time, so we want to cache the compiled
// regular expressions for performance purposes.
static std::array<std::pair<QString, QRegularExpression>, 50> regex_cache;
// Check if pattern is in cache
QString pattern{reinterpret_cast<const char*>(sqlite3_value_text(argv[0]))};
QRegularExpression regex;
const auto it = std::find_if(regex_cache.begin(), regex_cache.end(), [pattern](const std::pair<QString, QRegularExpression>& val) {
return val.first == pattern;
});
if(it == regex_cache.end())
{
// Pattern is not in cache. Create a new regular expressions object, compile it, and insert it into the cache
regex.setPattern(pattern);
if(!regex.isValid())
return sqlite3_result_error(ctx, "invalid operand", -1);
regex.optimize();
static size_t regex_cache_size;
regex_cache_size = (regex_cache_size + 1) % regex_cache.size();
regex_cache[regex_cache_size] = {pattern, regex};
} else {
// Pattern is in the cache. Just retrieve it
regex = it->second;
}
// Get arguments and check their values
QRegularExpression arg1(reinterpret_cast<const char*>(sqlite3_value_text(argv[0])));
if(!arg1.isValid())
return sqlite3_result_error(ctx, "invalid operand", -1);
QString arg2(reinterpret_cast<const char*>(sqlite3_value_text(argv[1])));
QString arg2{reinterpret_cast<const char*>(sqlite3_value_text(argv[1]))};
// Perform the actual matching and return the result.
// SQLite expects a 0 for not found and a 1 for found.
sqlite3_result_int(ctx, arg1.match(arg2).hasMatch());
sqlite3_result_int(ctx, regex.match(arg2).hasMatch());
}
bool DBBrowserDB::isOpen ( ) const