[YSQL] Fix org.yb.pgsql.TestYsqlUpgrade#migratingIsEquivalentToReinitdb test

[mdbridge]

Jira Link: DB-15025

Description

This test, run by:

ybd  --java-test 'org.yb.pgsql.TestYsqlUpgrade#migratingIsEquivalentToReinitdb'

fails if it is run on a operating system that has a different version of glibc from the version in the saved system catalog snapshot it compares against.

The error looks like:

[ERROR] migratingIsEquivalentToReinitdb(org.yb.pgsql.TestYsqlUpgrade)  Time elapsed: 88.813 s  <<< FAILURE!
java.lang.AssertionError: 
Table 'pg_collation': Column #11 (collversion) mismatch: expected:<2.39> but was:<2.28>
Expected row: Row[oid=java.lang.Long::1234567890,collname=java.lang.String::en_US,collnamespace=java.lang.Long::11,collowner=java.lang.Long::10,collprovider=java.lang.String::c,collisdeterministic=java.lang.Boolean::true,collencoding=java.lang.Integer::6,collcollate=java.lang.String::en_US.utf8,collctype=java.lang.String::en_US.utf8,colliculocale=null,collversion=java.lang.String::2.39]
Actual row:   Row[oid=java.lang.Long::1234567890,collname=java.lang.String::en_US,collnamespace=java.lang.Long::11,collowner=java.lang.Long::10,collprovider=java.lang.String::c,collisdeterministic=java.lang.Boolean::true,collencoding=java.lang.Integer::6,collcollate=java.lang.String::en_US.utf8,collctype=java.lang.String::en_US.utf8,colliculocale=null,collversion=java.lang.String::2.28]
	at org.yb.pgsql.TestYsqlUpgrade.lambda$assertMigrationsWorked$62(TestYsqlUpgrade.java:1897)
	at org.yb.pgsql.TestYsqlUpgrade.assertMigrationsWorked(TestYsqlUpgrade.java:1887)
	at org.yb.pgsql.TestYsqlUpgrade.migratingIsEquivalentToReinitdb(TestYsqlUpgrade.java:1076)

Here the operating system the test is being run on has glibc version 2.39 but the snapshot was made on a system with 2.28.

You can easily find out the glibc version by the following command:

$ ldd --version
ldd (GNU libc) 2.28

The code that takes this version and puts it in pg_collation table is:

~/code/yugabyte-db/src/postgres/src/backend/utils/adt/pg_locale.c:1716:
		/* Use the glibc version because we don't have anything better. */
		collversion = pstrdup(gnu_get_libc_version());

Probably fixing the test means making it ignore this field. For testing purposes, you can hardwire a different version above and it will make the test fail currently.

Issue Type

kind/bug

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[mdbridge]

Minghui Yang said:
Not obvious to me how to make the test change to ignore that field. That field is only set on Linux, so one work around is to avoid that code if in YB context, and we get same behavior on Mac and Linux. It does have the risk of missing the version mismatch check when running pg_upgrade, but en_US.utf8 is a common collation which may not easily subject to libc version changes so I think it is quite stable. None of the other libc collations are supported by YB.