storage did not release memory

[cangfengzhs]

Describe the bug (required)

All of the Expression are allocated in ObjectPool. And, when creating a tag/edge who contain a prop with a default value, the default value is stored as an Expressoin in Schema.

In graphd, the ObjectPool is created in every query, and released after query. But, in MetaClient, the pool is created when load schema, and released when reload schema if there is any update about schema. So, if schema is never never updated, the pool will never be released.

When writing any data who has a default value and ngql not fill it, storaged will compute default value. But, the Expression about default value will be clone and allocated in MetaClient's pool. This causes the pool to take up more and more memory, and it will never be released unless the schema is changed.

[Shylock-Hg]

But, the Expression about default value will be clone and allocated in MetaClient's pool.
Why need clone it?

[cangfengzhs]

I'm not sure if Expression is stateful. If it is not, clone is really not needed.

[Shylock-Hg]

I'm not sure if Expression is stateful. If it is not, clone is really not needed.

It's stateful. Expression will store the evaluate result to get performance improvement.

[cangfengzhs]

In addition, if the schema is updated and reloaded during the use of the default value, there will be a concurrency safety problem. The memory pointed to by Expression* in default value may have been released

[cangfengzhs]

It's stateful. Expression will store the evaluate result to get performance improvement.

So, clone is needed. Multi thread may be evaluate expression at same time