IGNITE-28795 Document SizeUsedByData metric#13247
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| You can also get an estimate of the actual size of data by multiplying the number of link:memory-architecture#data-pages[data pages] in use by the fill factor. The fill factor is the ratio of the size of data in a page to the page size, averaged over all pages. The number of pages in use and the fill factor are available at the level of data <<Data Region Size,region metrics>>. | ||
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| For link:memory-configuration/data-regions[data region] metrics, Ignite also exposes the `SizeUsedByData` metric. It estimates how many bytes are currently occupied by data in the region, including the empty space inside non-empty pages. Use this metric when you need a more direct estimate of how much data is stored in the region, and use `TotalAllocatedSize` when you need to monitor how much space has already been allocated for that region. |
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Previous paragraph is not quite correct. Fill factor is calculated only for used pages. So correct formula will be (total allocated - empty pages) * fill factor. This is exactly how SizeUsedByData is calculated. So this paragraph describes the almost the same entity as previous paragraph but using dedicated metric. I think we can unify both paragraphs (delete previous one and describe what is fill factor and how SizeUsedByData is calculated).
| | Attribute | Type | Description | Scope | ||
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| | TotalAllocatedSize | long | The size of the space allocated for this data region (in bytes). {allocsize_note} | Node | ||
| | SizeUsedByData | long | The estimated number of bytes occupied by data in this data region, including empty space inside non-empty pages. | Node |
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including empty space inside non-empty pages is confusing. Someone may think that empty space is added to this metric too. Maybe taking into account empty space inside non-empty pages?
| |PagesWritten| long| Number of pages written from last restart. | ||
| |PhysicalMemoryPages| long| Number of pages residing in physical RAM. | ||
| |PhysicalMemorySize | long| Gets total size of pages loaded to the RAM, in bytes | ||
| |SizeUsedByData| long| Estimated number of bytes occupied by data in the region, including empty space inside non-empty pages. |
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Tha same comment for including
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| | TotalAllocatedSize | long | The size of the space allocated for this data region (in bytes). {allocsize_note} | Node | ||
| | SizeUsedByData | long | The estimated number of bytes occupied by data in this data region, including empty space inside non-empty pages. | Node | ||
| | PagesFillFactor| float | The average amount of data in pages as a ratio of the page size. | Node |
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Lat's also clarify here something like in non-empty pages
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