Hi, Attached is an updated version of this patch series. It's meant to be applied on top of the 2pc decoding patch [1], because streaming of in-progress transactions requires handling of concurrent aborts. So it may or may not apply directly to master, I'm not sure - unfortunately that's likely to confuse the cputube thing, but I don't want to include the 2pc decoding bits here because that would be just confusing.
If needed, the part introducing logical_work_mem limit for ReorderBuffer can be separated and committed independently, but I do expect this to be committed after the 2pc decoding patch so I've left it like this. This new version is mostly just a rebase to current master (or almost, because 2pc decoding only applies to 29180e5d78 due to minor bitrot), but it also addresses the new stuff committed since last version (most importantly decoding of TRUNCATE). It also fixes a bug in WAL-logging of subxact assignments, where the assignment was included in records with XID=0, essentially failing to track the subxact properly. For the logical_work_mem part, I think this is quite solid. The main question is how to pick transactions for eviction. For now it uses the same approach as master (i.e. picking the largest top-level transaction, although measured by amount of memory and not just number of changes). But I've realized that may not work with Generation context that great, because unlike AllocSet it does not reuse the memory. That's nice as it allows freeing old blocks (which AllocSet can't), but it means a small transaction can have a change on old blocks preventing free(). That is something we have in pg11 already, because that's where Generation context got introduced - I haven't seen this issue in practice, but we might need to do something about it. In any case, I'm thinking we may need to pick a different eviction algorithm - say using a transaction with the oldest change (and loop until we release at least one block in the Generation context), or maybe look for block mixing changes from the smallest number of transactions, or something like that. Other ideas are welcome. I don't think the exact algorithm is particularly critical, because it's meant to be triggered only very rarely (i.e. pick logical_work_mem high enough). The in-progress streaming is mostly mechanical extension of existing functionality (new methods in various APIs, ...) and refactoring of ReorderBuffer to handle incremental decoding. I'm sure it'd benefit from reviews, of course. regards -- Tomas Vondra http://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
0001-Add-logical_work_mem-to-limit-ReorderBuffer-20181216.patch.gz
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0002-Immediately-WAL-log-assignments-20181216.patch.gz
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0003-Issue-individual-invalidations-with-wal_lev-20181216.patch.gz
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0004-Extend-the-output-plugin-API-with-stream-me-20181216.patch.gz
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0005-Implement-streaming-mode-in-ReorderBuffer-20181216.patch.gz
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0006-Add-support-for-streaming-to-built-in-repli-20181216.patch.gz
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0007-Track-statistics-for-streaming-spilling-20181216.patch.gz
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0008-BUGFIX-set-final_lsn-for-subxacts-before-cl-20181216.patch.gz
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