On Thu, Jun 20, 2024 at 3:23 AM Dmitry O Litvintsev <litvinse@xxxxxxxx> wrote:
Hello,
I am in the process of migrating DB to Alma9 host. The databse
is rather large - few TBs.
I have run pg_basebackup on Alma9 host and established replication from production to it. The idea is to quickly switch from master to this new host during downtime.
Establishing replication went fine. Source postgresql version is 15.6, destination is 15.7
When I psql into replica I get:
WARNING: database "xxx" has a collation version mismatch
DETAIL: The database was created using collation version 2.17, but the operating system provides version 2.34.
HINT: Rebuild all objects in this database that use the default collation and run ALTER DATABASE xxx REFRESH COLLATION VERSION, or build PostgreSQL with the right library version.
Looking up the issue the solution seems to be
REINDEX database xxx
ALTER DATABASE xxx REFRESH COLLATION VERSION
But this defeats the whole idea of having short downtime because REINDEX will take forever.
What is this "or build PostgreSQL with the right library version"?
Is this about 15.7 vs 15.6 or is it about different glibc version between RH7 and Alma9?
Is there a better way to handle it? I cannot afford long downtime.
You "only" need to REINDEX indices with TEXT (including CHAR and VARCHAR) columns. That may be most of your indices, or very few.
I use this view and query to find such indices:
create or replace view dba.all_indices_types as
select tbcl.relnamespace::regnamespace::text||'.'||tbcl.relname as table_name
, ndcl.relname as index_name
, array_agg(ty.typname order by att.attnum) as index_types
from pg_class ndcl
inner join pg_index nd
on (ndcl.oid = nd.indexrelid and ndcl.relkind = 'i')
inner join pg_class tbcl
on (nd.indrelid = tbcl.oid and tbcl.relkind = 'r')
inner join pg_attribute att
on att.attrelid = nd.indexrelid
inner join pg_type ty
on att.atttypid = ty.oid
where tbcl.relnamespace::regnamespace::text != 'pg_catalog'
group by tbcl.relnamespace::regnamespace::text||'.'||tbcl.relname
, ndcl.relname
order by 1, 2;
select tbcl.relnamespace::regnamespace::text||'.'||tbcl.relname as table_name
, ndcl.relname as index_name
, array_agg(ty.typname order by att.attnum) as index_types
from pg_class ndcl
inner join pg_index nd
on (ndcl.oid = nd.indexrelid and ndcl.relkind = 'i')
inner join pg_class tbcl
on (nd.indrelid = tbcl.oid and tbcl.relkind = 'r')
inner join pg_attribute att
on att.attrelid = nd.indexrelid
inner join pg_type ty
on att.atttypid = ty.oid
where tbcl.relnamespace::regnamespace::text != 'pg_catalog'
group by tbcl.relnamespace::regnamespace::text||'.'||tbcl.relname
, ndcl.relname
order by 1, 2;
select *
from dba.all_indices_types
where index_types && '{"text","varchar","char"}';
