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When auto caching is disabled

Code Block

language	java
title	Auto caching is disabled

TableEnvironment tEnv = ...
Table t1 = ...
Table t2 = t1.cache()
...
tEnv.execute() // t1 is cached.
Table t3 = t1.select(...) // cache will NOT be used. <----- difference
Table t4 = t2.select(...) // cache will be used.
...
// The following two lines of code are equivalent
t1.invalidateCache() // cache will be released
t2.invalidateCache() // cache will be released
...
// The following two lines of code are equivalent.
t1.print() // cache will not be recreated <-------- different
t2.print() // cache will be recreated

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Code Block

language	java
title	Semantic API Option 1

// Do not return anything
void cache();
// Alternatively, return the original table for chaining purpose.
Table cache();
 
// Physically uncache the table to release resource
void uncache();
 
// To explicitly ignore cache, not part of this proposal but in the future
Table hint(“ingoreCache”)

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Side effect: a table may be cached / uncached in a method invocation, while the caller does not know about this.

Code Block

language	java
title	Semantic Side Effect Option 1

{
  Table t  = …
   // cache the table
   t.cache(); 
   ...
   // The cache may be released in foo()
   foo(t);
   ...
   // cache is no longer available
   t.bar() 
}
 
 
void foo(Table t) {
   // cache the table
   t.cache();   
   ….
   // Physically drop the table
   t.uncache(); 
}

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Code Block

language	java
title	Semantic API Option 2

// Return CachedTable
CachedTable cache();
 
public interface CachedTable extends Table {
  // Physically uncache the table to release resource
  void uncache();
}

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Code Block

language	java
title	Semantic API Option 3

// Return a CacheHandle
CacheHandle cache();
 
public interface CacheHandle {
  // Physically release cache resource
  void release();
}

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Code Block

language	java
title	Semantic Option 23

TableEnvironment tEnv = ...
Table t = …
...
// cache the table
CacheHandle handle1 = t.cache();
CacheHandle handle2 = t.cache;
…
// Assume some execution physically created the cache.
tEnv.execute()
...
// Optimizer decide whether cache will be used.
t.foo();
...
// Release the first handle, cache will not be released because handle 2 has not been released
handle1.release();
// Release the second handle, the cache will be released because all the cache handle have been released.
handle2.release();

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Versions Compared

Old Version 3

New Version 4

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