GitHub user vovik0134 added a comment to the discussion: [Ideas] Description of
backward-incompatible changes between Greenplum 6 and Cloudberry in the
documentation.
Backward-incompatible changes in the system catalog and metadata were also
identified.
## Changes in the system catalog and metadata
### Removed and renamed columns in system catalog views and tables
When moving to Cloudberry, together with the PostgreSQL kernel and Greenplum 6
upgrade, the following columns in system catalog views and tables were removed
or renamed:
| Old column |
New column |
|-----------------------------------------------------------------------------|----------------------------------------------------------------------|
| `pg_class.relhasoids` |
Removed |
| `pg_class.relhaspkey` |
`EXISTS (SELECT FROM pg_index WHERE indrelid=... AND indisprimary)` |
| `pg_class.relstorage` |
`pg_class.relam` |
| `pg_proc.proisagg` |
`pg_proc.prokind = 'a'` |
| `pg_proc.proiswindow` |
`pg_proc.prokind = 'w'` |
| `pg_proc.protransform` |
`pg_proc.prosupport` |
| `pg_attrdef.adsrc` |
`pg_get_expr(adbin, adrelid)` |
| `pg_constraint.consrc`
| `pg_get_constraintdef(oid)` |
| `pg_stat_activity.waiting` |
`wait_event_type`, `wait_event` |
| `pg_am.*` — dozens of columns |
The access method API has been significantly reworked. There is no simple
replacement. |
| `gp_distributed_log.distributed_id`, `gp_distributed_xacts.distributed_id` |
Removed |
| `gp_stat_replication.*_location` |
Renamed to `*_lsn` |
| `information_schema.routines.result_cast_character_set_name` |
Renamed to `result_cast_char_set_name` |
**How to detect**
Check the application codebase for uses of removed or renamed columns.
**How to fix**
Make the corresponding changes in the application codebase.
### Removal of system tables and views
The following system tables and views have been completely removed in
Cloudberry compared to Greenplum 6:
* `pg_catalog.pg_partition`;
* `pg_catalog.pg_partition_columns`;
* `pg_catalog.pg_partition_encoding`;
* `pg_catalog.pg_partition_rule`;
* `pg_catalog.pg_partitions`;
* `pg_catalog.pg_partition_templates`;
* `pg_catalog.pg_stat_partition_operations`.
**How to detect**
Check the application codebase for uses of the removed system tables and views.
**How to fix**
Make the corresponding changes in the application codebase.
To work with partitioned tables in Cloudberry, use the `pg_partitioned_table`
view and the `pg_partition_tree()`, `pg_partition_ancestors()`, and
`pg_partition_root()` functions.
### Removal and renaming of system functions
The following system functions have been completely removed in Cloudberry
compared to Greenplum 6:
* `pg_get_partition_def`, `pg_get_partition_rule_def`,
`pg_get_partition_template_def`;
* `gp_elog`, `gp_fault_inject`, `gp_update_ao_master_stats`.
Functions in the `pg_*_xlog*` family have been renamed according to the
`pg_*_wal*` pattern, for example, `pg_switch_xlog()` → `pg_switch_wal()`.
Some functions have been removed.
**How to detect**
Check the application codebase for uses of removed and renamed system functions.
**How to fix**
Make the corresponding changes in the application codebase.
### Changes in how sequence metadata is displayed
Starting with PostgreSQL kernel version 10, the way sequence metadata is
displayed has changed.
Queries of the form `SELECT * FROM <seq_name>` now return only `last_value`,
`log_cnt`, and `is_called`. Other properties are available through
`pg_sequence` or `pg_sequences`.
Example for Greenplum 6:
```sql
CREATE SEQUENCE example_seq
START WITH 100
INCREMENT BY 1;
SELECT * FROM example_seq;
sequence_name | last_value | start_value | increment_by | max_value
| min_value | cache_value | log_cnt | is_cycled | is_called
------------------+------------+-------------+--------------+---------------------+-----------+-------------+---------+-----------+-----------
example_seq | 100 | 100 | 1 |
9223372036854775807 | 1 | 1 | 0 | f | f
```
Example for Cloudberry:
```sql
CREATE SEQUENCE example_seq
START WITH 100
INCREMENT BY 1;
SELECT * FROM example_seq;
last_value | log_cnt | is_called
------------+---------+-----------
100 | 0 | f
SELECT * FROM pg_sequence WHERE seqrelid = 'example_seq'::regclass;
seqrelid | seqtypid | seqstart | seqincrement | seqmax | seqmin |
seqcache | seqcycle
----------+----------+----------+--------------+---------------------+--------+----------+----------
17186 | 20 | 100 | 1 | 9223372036854775807 | 1 |
20 | f
SELECT * FROM pg_sequences WHERE sequencename = 'example_seq';
schemaname | sequencename | sequenceowner | data_type | start_value |
min_value | max_value | increment_by | cycle | cache_size | last_value
------------+-----------------+---------------+-----------+-------------+-----------+---------------------+--------------+-------+------------+------------
public | example_seq | user1 | bigint | 100 |
1 | 9223372036854775807 | 1 | f | 20 |
```
**How to detect**
Check the application codebase for queries of the form `SELECT * FROM
<seq_name>` that use fields other than `last_value`, `log_cnt`, and `is_called`.
**How to fix**
Make the corresponding changes in the application codebase by querying
`pg_sequence` or `pg_sequences`.
### Change in the internal representation of external tables
Inside Cloudberry, external tables are represented as foreign tables. Compared
to Greenplum 6, this results in the following differences:
* The `pg_tables` system view no longer shows external tables.
* `pg_class.relkind` for external tables is now `'f'`, not `'r'`.
* The `pg_exttable` system table has become a view.
* The `EXPLAIN` output has changed: `Foreign Scan` is displayed instead of
`External Scan`.
**How to detect**
Check the application codebase and scripts for references to external table
metadata.
The list of external tables can be obtained with the following query:
```sql
SELECT n.nspname, c.relname, c.relkind, e.urilocation, e.execlocation,
e.fmttype, e.fmtopts
FROM pg_exttable e
JOIN pg_class c ON c.oid = e.reloid
JOIN pg_namespace n ON n.oid = c.relnamespace;
```
**How to fix**
Make changes to the application codebase and scripts according to these changes.
### The `gp_toolkit` schema is now provided as an extension
In Cloudberry, unlike Greenplum 6, `gp_toolkit` is provided as an extension.
>From an installation perspective, nothing changes: when a database is created,
>`gp_toolkit` is connected automatically.
The following views have been removed:
* `gp_toolkit.gp_size_of_partition_and_indexes_disk`;
* `gp_toolkit.__gp_user_data_tables`.
The signatures of the following existing functions have changed:
* `gp_toolkit.__gp_aoseg*`;
* `gp_toolkit.__gp_aocsseg*`;
* `gp_dist_wait_status`;
* `gp_execution_segment`;
* `gp_request_fts_probe_scan`;
* `gp_tablespace_segment_location`.
The following columns have been removed from existing views:
* `gp_toolkit.gp_locks_on_resqueue.lorwaiting`;
* `gp_toolkit.gp_resgroup_config.cpu_rate_limit`;
* `gp_toolkit.gp_resgroup_config.memory_auditor`;
* `gp_toolkit.gp_resgroup_config.memory_shared_quota`;
* `gp_toolkit.gp_resgroup_config.memory_spill_ratio`;
* `gp_toolkit.gp_resgroup_status.cpu_usage`;
* `gp_toolkit.gp_resgroup_status.memory_usage`;
* `gp_toolkit.gp_resgroup_status_per_host.cpu`;
* `gp_toolkit.gp_resgroup_status_per_host.memory_available`;
* `gp_toolkit.gp_resgroup_status_per_host.memory_quota_available`;
* `gp_toolkit.gp_resgroup_status_per_host.memory_quota_used`;
* `gp_toolkit.gp_resgroup_status_per_host.memory_shared_available`;
* `gp_toolkit.gp_resgroup_status_per_host.memory_shared_used`;
* `gp_toolkit.gp_resgroup_status_per_host.memory_used`;
* `gp_toolkit.gp_resgroup_status_per_host.rsgname`;
* `gp_toolkit.gp_resgroup_status_per_segment.cpu`;
* `gp_toolkit.gp_resgroup_status_per_segment.hostname`;
* `gp_toolkit.gp_resgroup_status_per_segment.memory_available`;
* `gp_toolkit.gp_resgroup_status_per_segment.memory_quota_available`;
* `gp_toolkit.gp_resgroup_status_per_segment.memory_quota_used`;
* `gp_toolkit.gp_resgroup_status_per_segment.memory_shared_available`;
* `gp_toolkit.gp_resgroup_status_per_segment.memory_shared_used`;
* `gp_toolkit.gp_resgroup_status_per_segment.memory_used`;
* `gp_toolkit.gp_resgroup_status_per_segment.rsgname`;
* `gp_toolkit.gp_resgroup_status.rsgname`;
* `gp_toolkit.__gp_user_tables.autrelstorage`.
**How to detect**
Check the application codebase and scripts for uses of changed or removed
objects.
**How to fix**
Adapt the application codebase and scripts: stop using removed objects and
account for changes in existing ones.
GitHub link:
https://github.com/apache/cloudberry/discussions/1816#discussioncomment-17260347
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