Horton

Re: PATCH: logical_work_mem and logical streaming of large in-progress transactions

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Dilip Kumar <dilipbalaut@gmail.com>
Cc: Kuntal Ghosh <kuntalghosh.2007@gmail.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Michael Paquier <michael@paquier.xyz>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2020-04-28T09:41:27Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Tighten the concurrent abort check during decoding.

  2. Improve hash_create()'s API for some added robustness.

  3. Use HASH_BLOBS for xidhash.

  4. Fix initialization of RelationSyncEntry for streaming transactions.

  5. Remove unused function declaration in logicalproto.h.

  6. Add additional tests to test streaming of in-progress transactions.

  7. Fix inline marking introduced in commit 464824323e.

  8. Add support for streaming to built-in logical replication.

  9. Fix the SharedFileSetUnregister API.

  10. Fix comment in procarray.c

  11. Suppress compiler warning in non-cassert builds.

  12. Extend the BufFile interface.

  13. Mark a few logical decoding related variables with PGDLLIMPORT.

  14. Implement streaming mode in ReorderBuffer.

  15. Extend the logical decoding output plugin API with stream methods.

  16. WAL Log invalidations at command end with wal_level=logical.

  17. Immediately WAL-log subtransaction and top-level XID association.

  18. Allow logical replication to transfer data in binary format.

  19. Only superuser can set sslcert/sslkey in postgres_fdw user mappings

  20. Track statistics for spilling of changes from ReorderBuffer.

  21. Add logical_decoding_work_mem to limit ReorderBuffer memory usage.

  22. logical decoding: process ASSIGNMENT during snapshot build

  23. Emit invalidations to standby for transactions without xid.

On Mon, Apr 27, 2020 at 4:05 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
>
[latest patches]

v16-0004-Gracefully-handle-concurrent-aborts-of-uncommitt
-     Any actions leading to transaction ID assignment are prohibited.
That, among others,
+     Note that access to user catalog tables or regular system catalog tables
+     in the output plugins has to be done via the
<literal>systable_*</literal> scan APIs only.
+     Access via the <literal>heap_*</literal> scan APIs will error out.
+     Additionally, any actions leading to transaction ID assignment
are prohibited. That, among others,
..
@@ -1383,6 +1392,14 @@ heap_fetch(Relation relation,
  bool valid;

  /*
+ * We don't expect direct calls to heap_fetch with valid
+ * CheckXidAlive for regular tables. Track that below.
+ */
+ if (unlikely(TransactionIdIsValid(CheckXidAlive) &&
+ !(IsCatalogRelation(relation) || RelationIsUsedAsCatalogTable(relation))))
+ elog(ERROR, "unexpected heap_fetch call during logical decoding");
+

I think comments and code don't match.  In the comment, we are saying
that via output plugins access to user catalog tables or regular
system catalog tables won't be allowed via heap_* APIs but code
doesn't seem to reflect it.  I feel only
TransactionIdIsValid(CheckXidAlive) is sufficient here.  See, the
original discussion about this point [1] (Refer "I think it'd also be
good to add assertions to codepaths not going through systable_*
asserting that ...").

Isn't it better to block the scan to user catalog tables or regular
system catalog tables for tableam scan APIs rather than at the heap
level?  There might be some APIs like heap_getnext where such a check
might still be required but I guess it is still better to block at
tableam level.

[1] - https://www.postgresql.org/message-id/20180726200241.aje4dv4jsv25v4k2%40alap3.anarazel.de

-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com