| [HINT_LOCAL] |
[1] |
Obtains only the calculation results on the
local server |
in a distributed cluster |
select [HINT_LOCAL] sum(*) from pt |
| [HINT_HASH] |
[32] |
Groups data with the hash algorithm by
default |
with a group by clause |
select [HINT_HASH] count(*) from t group by
sym |
| [HINT_SNAPSHOT] |
[64] |
Queries data from a snapshot engine of a DFS
table |
when querying a snapshot engine registered
with registerSnapshotEngine |
select [HINT_SNAPSHOT] * from
loadTable(dbName,tableName) |
| [HINT_KEEPORDER] |
[128] |
Keeps the order of output records consistent
with the input |
with a context by clause |
select [HINT_KEEPORDER] cumsu(vol) from t
context by date, sym |
| [HINT_SEQ] |
[512] |
Executes queries on partitions serially to
save the concurrency overhead |
when memory is limited |
timer select [HINT_SEQ] avg(vol) from
t |
| [HINT_NOMERGE] |
[1024] |
Skips the merge step of intermediate results
from map clause to improve the performance. Instead of returning the
merged results in an in-memory table, only the handles of DFS tables are
returned. |
when the intermediate results do not need to
be returned |
select [HINT_NOMERGE] price from pt context by
ticker |
| [HINT_PRELOAD] |
[4096] |
Loads all data into memory before filtering
with where-conditions. Only supported in TSDB engine. |
with a where clause |
select [HINT_PRELOAD] sum(price) from t where
volume > 100000 |
| [HINT_EXPLAIN] |
[32768] |
Prints the query execution plan to monitor the
real-time performance and execution order of a SQL query |
for SQL performance tuning. See
[HINT_EXPLAIN] |
select [HINT_EXPLAIN] * from tb where id >
20 |
| [HINT_SORT] |
[524288] |
Applies sorting algorithm to data
grouping |
with a group by clause |
select [HINT_SORT] avg(price) from trades
group by sym |
| [HINT_VECTORIZED] |
[4194304] |
Applies vectorization to data grouping |
with a group by clause |
select [HINT_VECTORIZED] sum(price) from
trades group by sym |
