76 lines
2.7 KiB
MySQL
76 lines
2.7 KiB
MySQL
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/*+ hint [ , ... ] */
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SELECT /*+ COALESCE(3) */ * FROM t;
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SELECT /*+ REPARTITION(3) */ * FROM t;
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SELECT /*+ REPARTITION(c) */ * FROM t;
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SELECT /*+ REPARTITION(3, c) */ * FROM t;
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SELECT /*+ REPARTITION_BY_RANGE(c) */ * FROM t;
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SELECT /*+ REPARTITION_BY_RANGE(3, c) */ * FROM t;
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SELECT /*+ REBALANCE */ * FROM t;
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SELECT /*+ REBALANCE(3) */ * FROM t;
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SELECT /*+ REBALANCE(c) */ * FROM t;
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SELECT /*+ REBALANCE(3, c) */ * FROM t;
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-- multiple partitioning hints
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EXPLAIN EXTENDED SELECT /*+ REPARTITION(100), COALESCE(500), REPARTITION_BY_RANGE(3, c) */ * FROM t;
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-- == Parsed Logical Plan ==
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-- 'UnresolvedHint REPARTITION, [100]
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-- +- 'UnresolvedHint COALESCE, [500]
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-- +- 'UnresolvedHint REPARTITION_BY_RANGE, [3, 'c]
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-- +- 'Project [*]
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-- +- 'UnresolvedRelation [t]
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-- == Analyzed Logical Plan ==
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-- name: string, c: int
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-- Repartition 100, true
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-- +- Repartition 500, false
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-- +- RepartitionByExpression [c#30 ASC NULLS FIRST], 3
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-- +- Project [name#29, c#30]
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-- +- SubqueryAlias spark_catalog.default.t
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-- +- Relation[name#29,c#30] parquet
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-- == Optimized Logical Plan ==
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-- Repartition 100, true
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-- +- Relation[name#29,c#30] parquet
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-- == Physical Plan ==
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-- Exchange RoundRobinPartitioning(100), false, [id=#121]
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-- +- *(1) ColumnarToRow
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-- +- FileScan parquet default.t[name#29,c#30] Batched: true, DataFilters: [], Format: Parquet,
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-- Location: CatalogFileIndex[file:/spark/spark-warehouse/t], PartitionFilters: [],
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-- PushedFilters: [], ReadSchema: struct<name:string>
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-- Join Hints for broadcast join
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SELECT /*+ BROADCAST(t1) */ * FROM t1 INNER JOIN t2 ON t1.key = t2.key;
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SELECT /*+ BROADCASTJOIN (t1) */ * FROM t1 left JOIN t2 ON t1.key = t2.key;
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SELECT /*+ MAPJOIN(t2) */ * FROM t1 right JOIN t2 ON t1.key = t2.key;
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-- Join Hints for shuffle sort merge join
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SELECT /*+ SHUFFLE_MERGE(t1) */ * FROM t1 INNER JOIN t2 ON t1.key = t2.key;
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SELECT /*+ MERGEJOIN(t2) */ * FROM t1 INNER JOIN t2 ON t1.key = t2.key;
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SELECT /*+ MERGE(t1) */ * FROM t1 INNER JOIN t2 ON t1.key = t2.key;
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-- Join Hints for shuffle hash join
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SELECT /*+ SHUFFLE_HASH(t1) */ * FROM t1 INNER JOIN t2 ON t1.key = t2.key;
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-- Join Hints for shuffle-and-replicate nested loop join
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SELECT /*+ SHUFFLE_REPLICATE_NL(t1) */ * FROM t1 INNER JOIN t2 ON t1.key = t2.key;
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-- When different join strategy hints are specified on both sides of a join, Spark
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-- prioritizes the BROADCAST hint over the MERGE hint over the SHUFFLE_HASH hint
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-- over the SHUFFLE_REPLICATE_NL hint.
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-- Spark will issue Warning in the following example
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-- org.apache.spark.sql.catalyst.analysis.HintErrorLogger: Hint (strategy=merge)
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-- is overridden by another hint and will not take effect.
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SELECT /*+ BROADCAST(t1), MERGE(t1, t2) */ * FROM t1 INNER JOIN t2 ON t1.key = t2.key;
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