schemeshard: fix copy-tables memory hog #1442
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Export launches copy-tables operation, copy-tables invokes multiple copy table suboperations, each copy-table suboperation grabs and saves aside metadata of table's subdomain (to be able to restore original subdomain state in case IgniteOperation() fails). Straightforward implementation of TMemChanges resulted in that the same and only subdomain being copied multiple times. Which for massive export actions with many-many tables copied is both cpu intensive and, more importantly, requires excessive amount of memory (up to several observed OOM events). This fix changes TMemChanges to store only one subdomain state version per operation. Which is correct and appropriate for copy-tables and all other (sub)operations. KIKIMR-20242
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snaury
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Jan 31, 2024
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Changelog entry
Fix excessive memory requirements for backing up databases with massive amount of tables.
Changelog category
Additional information
Simplified tracking of in-memory schema state in schemeshard captured too many copies of database metadata objects during database export/backup.
KIKIMR-20242