Cheng Lian created SPARK-1669:
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Summary: SQLContext.cacheTable() should be idempotent
Key: SPARK-1669
URL: https://issues.apache.org/jira/browse/SPARK-1669
Project: Spark
Issue Type: Improvement
Components: SQL
Affects Versions: 1.0.0
Reporter: Cheng Lian
Calling {{cacheTable()}} on some table {{t} multiple times causes table {{t}}
to be cached multiple times. This semantics is different from {{RDD.cache()}},
which is idempotent.
We can check whether a table is already cached by checking:
# whether the structure of the underlying logical plan of the table is matches
the pattern {{Subquery(\_, SparkLogicalPlan(inMem @
InMemoryColumnarTableScan(_, _)))}}
# whether {{inMem.cachedColumnBuffers.getStorageLevel.useMemory}} is true
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