Re: reindex option for tuning load large data

On Fri, Jun 17, 2022 at 1:34 AM James Pang (chaolpan) <chaolpan(at)cisco(dot)com>
wrote:

> Hi ,
>
> We plan to migrate large database from Oracle to Postgres(version 13.6,
> OS Redhat8 Enterprise), we are checking options to make data load in
> Postgres fast. Data volume is about several TB, thousands of indexes,
> many large table with partitions. We want to make data load running fast
> and avoid miss any indexes when reindexing. There are 2 options about
> reindex. Could you give some suggestions about the 2 options, which option
> is better.
>
>
>
> 1. Create tables and indexes( empty database) , update pg_index set
> indisready=false and inisvalid=false, then load data use COPY from csv ,
> then reindex table …
>
>
Where did this idea come from? This is likely to destroy your database.

> 2). Use pg_dump to dump meta data only , then copy “CREATE INDEX … sql “
>
> Drop indexes before data load
>
> After data load, increase max_parallel_maintenance_workers,
> maintenance_work_mem
>
> Run CREATE INDEX … sql to leverage parallel create index feature.
>

pg_dump doesn't run against Oracle, so where is the thing you are running
pg_dump against coming from?

If you already have a fleshed out schema in PostgreSQL, you should dump the
sections separately (with --section=pre-data and --section=post-data) to
get the commands to build the objects which should be run before and after
the data is loaded.

Cheers,

Jeff

>