TD Trino Query Optimizer

Output Optimization

CTAS is 5x faster than SELECT (skips JSON serialization):

create table results as
select td_time_string(time, 'd!', 'JST') as date, count(*) as events
from events
where td_interval(time, '-1M', 'JST')
group by 1

User-Defined Partitioning (UDP)

Hash partition for fast ID lookups on large tables (>100M rows):

create table customer_events with (
  bucketed_on = array['customer_id'],
  bucket_count = 512
) as
select * from raw_events
where td_interval(time, '-30d', 'JST')

Accelerated queries (equality on all bucketing columns):

select * from customer_events
where customer_id = 12345
  and td_interval(time, '-7d', 'JST')

NOT accelerated (missing bucketing column):

select * from customer_events
where td_interval(time, '-7d', 'JST')

UDP for colocated joins:

-- set session join_distribution_type = 'PARTITIONED'
-- set session colocated_join = 'true'
select a.*, b.*
from customer_events_a a
join customer_events_b b on a.customer_id = b.customer_id

Magic Comments for Join Distribution

-- BROADCAST: Small right table fits in memory
-- set session join_distribution_type = 'BROADCAST'
select * from large_table, small_lookup
where large_table.id = small_lookup.id

-- PARTITIONED: Both tables large or memory issues
-- set session join_distribution_type = 'PARTITIONED'
select * from large_table_a, large_table_b
where large_table_a.id = large_table_b.id

REGEXP_LIKE vs Multiple LIKE

-- BAD: Multiple LIKE clauses
where column like '%android%' or column like '%ios%' or column like '%mobile%'

-- GOOD: Single REGEXP_LIKE
where regexp_like(column, 'android|ios|mobile')

Approximate Functions

approx_distinct(user_id)              -- vs count(distinct user_id)
approx_percentile(response_time, 0.95)
approx_set(column)                    -- HyperLogLog sketch

~2% error rate, dramatically reduced memory.

Common Errors

Error	Fix
Query exceeded memory limit	Narrow time range, use approx functions, try PARTITIONED join
PAGE_TRANSPORT_TIMEOUT	Reduce columns, use CTAS, process in smaller chunks
Query timeout	Add time filters, use limit for testing

Optimization Checklist

• Time filter (td_interval/td_time_range)
• Specific columns (not select *)
• approx_distinct for unique counts
• regexp_like for pattern matching
• CTAS for large results
• UDP for frequent ID lookups