Am 03.01.22 um 22:03 schrieb Justin Pryzby:
+pgstat_report_toast_activity(Oid relid, int attr,
+ bool externalized,
+ bool compressed,
+ int32 old_size,
+ int32 new_size,
...
+ if (new_size)
+ {
+ htabent->t_counts.t_size_orig+=old_size;
+ if (new_size)
+ {
I guess one of these is supposed to say old_size?
Didn't make a difference, tbth, as they'd both be 0 or have a value.
Streamlined the whole block now.
+CREATE TABLE toast_test (cola TEXT, colb TEXT COMPRESSION lz4, colc TEXT ,
cold TEXT, cole TEXT);
Is there a reason this uses lz4 ?
I thought it might help later on, but alas! the LZ4 column mainly broke
things, so I removed it for the time being.
If that's needed for stable results, I think you should use pglz, since that's
what's guaranteed to exist. I imagine LZ4 won't be required any time soon,
seeing as zlib has never been required.
Yeah. It didn't prove anything whatsoever.
+ Be aware that this feature, depending on the amount of TOASTable
columns in
+ your databases, may significantly increase the size of the statistics
files
+ and the workload of the statistics collector. It is recommended to only
+ temporarily activate this to assess the right compression and storage
method
+ for (a) column(s).
saying "a column" is fine
Changed.
+ <structfield>schemaname</structfield> <type>name</type>
+ Attribute (column) number in the relation
+ <structfield>relname</structfield> <type>name</type>
+ <entry role="catalog_table_entry"><para role="column_definition">
+ <structfield>compressmethod</structfield> <type>char</type>
+ </para>
+ <para>
+ Compression method of the attribute (empty means default)
One thing to keep in mind is that the current compression method is only used
for *new* data - old data can still use the old compression method. It
probably doesn't need to be said here, but maybe you can refer to the docs
about that in alter_table.
+ Number of times the compression was successful (gained a size reduction)
It's more clear to say "was reduced in size"
Changed the wording a bit, I guess it is clear enough now.
The question is if the column should be there at all, as it's simply
fetched from pg_attribute...
+ /* we assume this inits to all zeroes: */
+ static const PgStat_ToastCounts all_zeroes;
You don't have to assume; static/global allocations are always zero unless
otherwise specified.
Copy-pasta ;-)
Removed.
Thx for looking into this!
Patch v7 will be in the next mail.
--
Gunnar "Nick" Bluth
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Email: gunnar.bl...@pro-open.de
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