[PHOENIX-4974] Gets all regions uses get requests is extremely slows for big table

• Type: Improvement
• Status: Open
• Priority: Blocker
• Resolution: Unresolved
• Affects Version/s: 4.14.0, 5.0.0
• Assignee: Jaanai Zhang
• Reporter: Jaanai Zhang
• Created: 16/Oct/18 12:36
• Updated: 19/Oct/18 02:29

Description

When executes the first query after started the client(SQLline or initializing JDBC client ), needs to load region locations to the client cache. Now the following is key implement :

List<HRegionLocation> locations = Lists.newArrayList();
                byte[] currentKey = HConstants.EMPTY_START_ROW;
                do {
                    HRegionLocation regionLocation = connection.getRegionLocation(
                            TableName.valueOf(tableName), currentKey, reload);
                    locations.add(regionLocation);
                    currentKey = regionLocation.getRegionInfo().getEndKey();
                } while (!Bytes.equals(currentKey, HConstants.EMPTY_END_ROW));

For some big tables which have more than ten thousand regions, this procedure is extremely slow.

Runs a look points query on the table that has 10000 regions after starting the client, it needs 25+ seconds.