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Drasticly improve zoom tile calculation for larger maps when using MySQL storage engine. For Larger Tables doing Limit and Offset can have a big Impact on Statement execution because it is an IO heavy task.

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This fixes the issue by not doing any limit / offset on the SQL statement but instead query for all the data at once, and let the JDBC handler do the resultset handling.
This can probably be adapted for MSSQL, PostgreSQL and SQLLite.
This commit is contained in:
stormboomer 2023-08-28 08:03:43 +02:00
parent b310a57b64
commit 247e81bc61
1 changed files with 14 additions and 22 deletions
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36
DynmapCore/src/main/java/org/dynmap/storage/mysql/MySQLMapStorage.java
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@ -809,29 +809,21 @@ public class MySQLMapStorage extends MapStorage {
}
try {
c = getConnection();
boolean done = false;
int limit = 100;
int offset = 0;
while (!done) {
// Query tiles for given mapkey
Statement stmt = c.createStatement();
ResultSet rs = stmt.executeQuery(String.format("SELECT x,y,zoom,Format FROM %s WHERE MapID=%d LIMIT %d OFFSET %d;", tableTiles, mapkey, limit, offset));
int cnt = 0;
while (rs.next()) {
StorageTile st = new StorageTile(world, map, rs.getInt("x"), rs.getInt("y"), rs.getInt("zoom"), var);
final MapType.ImageEncoding encoding = MapType.ImageEncoding.fromOrd(rs.getInt("Format"));
if(cb != null)
cb.tileFound(st, encoding);
if(cbBase != null && st.zoom == 0)
cbBase.tileFound(st, encoding);
st.cleanup();
cnt++;
}
rs.close();
stmt.close();
if (cnt < limit) done = true;
offset += cnt;
Statement stmt = c.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY, //we want to stream our resultset one row at a time, we are not interessted in going back
java.sql.ResultSet.CONCUR_READ_ONLY); //since we do not handle the entire resultset in memory -> tell the statement that we are going to work read only
stmt.setFetchSize(100); //we can change the jdbc "retrieval chunk size". Basicly we limit how much rows are kept in memory. Bigger value = less network calls to DB, but more memory consumption
ResultSet rs = stmt.executeQuery(String.format("SELECT x,y,zoom,Format FROM %s WHERE MapID=%d;", tableTiles, mapkey)); //we do the query, but do not set any limit / offset. Since data is not kept in memory, just streamed from DB this should not be a problem, only the rows from setFetchSize are kept in memory.
while (rs.next()) {
StorageTile st = new StorageTile(world, map, rs.getInt("x"), rs.getInt("y"), rs.getInt("zoom"), var);
final MapType.ImageEncoding encoding = MapType.ImageEncoding.fromOrd(rs.getInt("Format"));
if(cb != null)
cb.tileFound(st, encoding);
if(cbBase != null && st.zoom == 0)
cbBase.tileFound(st, encoding);
st.cleanup();
}
rs.close();
stmt.close();
if(cbEnd != null)
cbEnd.searchEnded();
} catch (SQLException x) {