I created a table with monthly partitions, however I made a mistake with the initial partition.
When I browse the partitions in Data Grip it first one shows up as unnamed (see image)
However, when selecting the partition tables there is tabled for this partition, named abc_1_prt_2. All the other partitions' tables are named something like abc_1_prt_p202208
Is it possible to rename the unnamed partition?
When I right-click on partition in Data Grip and select Rename, Data Grip provides the following script:
alter table sam_tap.fct_tap_metadata rename partition "" to "'p201809'";
which gives the following error:
[42601] ERROR: zero-length delimited identifier at or near """"
ALTER TABLE "partition <unnamed1>'
RENAME TO whatever;
This assumes that there are no extra spaces anywhere in the name.
Just FYI, in the end I dropped the table and recreated it with the correct partition name (and populated the data from a back-up).
I was not able to re-name the unnamed partition.
Related
I have a postgres table (in postgres12) which is supposed to have thousands of partitions (200k at least) in near future.
Here is how I am creating the parent table:
create table if not exists content (
key varchar(20) not NULL,
value json not null default '[]'::json
) PARTITION BY LIST(key)
And then adding any given child tables like:
create table if not exists content_123 PARTITION OF content for VALUES in ('123');
Also I am adding an index on top of the child table for quick access (since I will be accessing the child table directly):
create index if not exists content_123_idx on content_123 using btree(key)
Here is my question: I have never in the past managed this many partitions in a postgres table so I am just wondering is there any downside of doing what I am doing? Also, (as mentioned above) I will not be querying from the parent table directly, but will read directly from individual child tables.
With these table definitions, the index is completely useless.
With 200000 partitions, query planning will become intolerably slow, and each SQL statement will need very many locks and open files. This won't work well.
Lump several keys together into a single partition (then the index might make sense).
I have a .csv file with ~300,000 rows, some of which violate certain constraints I set in my postgres database. Is there a way to copy my .csv file into the database and have postgres filter out the rows that violate the constraints? I do not want these rows to show up in the database.
If this is not possible, is there any other way to solve this problem?
what I'm doing right now is
COPY blocksequences from '/tmp/blocksequences.csv CSV HEADER;
And I get
'ERROR: new row for relation "blocksequences" violates check constraint "blocksequences_partid3_check"
DETAIL: Failing row contains (M001-M049-S186, M001, null, M049, S186).
CONTEXT: COPY blocksequences, line 680: "M001-M049-S186,M001,,M049,S186"
reason for the error: column that contains M049 is not allowed to have that string entered. Many other rows have violations like this.
I read a little about exception when check violation --do nothing am I on the right track here? seems like it's only a mysql thing maybe
Usually this is done in this way:
create a temporary table with the same structure as the destination one but without constraints,
copy data to the temporary table with COPY command,
copy rows that do fulfill constraints from temp table to the destination one, using INSERT command with conditions in the WHERE clause based on the table constraint,
drop the temporary table.
When dealing with really large CSV files or very limited server resources, use the extension file_fdw instead of temporary tables. It's much more efficient way but it requires server access to a CSV file (while copying to a temporary table can be done over the network).
In Postgres 12 you can use the WHERE clause in COPY FROM.
I am trying to use exchange partition knowledge module in ODI.
When I create two tables with different column order, exchange partitions is working correctly. But when I change column order with alter table script, exchange partition is giving this error:
SQL Error: ORA-14097: column type or size mismatch in ALTER TABLE EXCHANGE PARTITION
this code is giving above error:
ALTER TABLE schema1.CALLPARTITIONED EXCHANGE PARTITION call_partition WITH
TABLE schema2.CALL_TEMP WITHOUT VALIDATION;
I do not understand the difference between these two methods. Why does not it work correctly when I change table column order after create?
Thank you for your help.
I know how partitioning in DB2 works but I am unaware about where this partition values exactly get stored. After writing a create partition query, for example:
CREATE TABLE orders(id INT, shipdate DATE, …)
PARTITION BY RANGE(shipdate)
(
STARTING '1/1/2006' ENDING '12/31/2006'
EVERY 3 MONTHS
)
after running the above query we know that partitions are created on order for every 3 month but when we run a select query the query engine refers this partitions. I am curious to know where this actually get stored, whether in the same table or DB2 has a different table where partition value for every table get stored.
Thanks,
table partitions in DB2 are stored in tablespaces.
For regular tables (if table partitioning is not used) table data is stored in a single tablespace (not considering LOBs).
For partitioned tables multiple tablespaces can used for its partitions.
This is achieved by the "" clause of the CREATE TABLE statement.
CREATE TABLE parttab
...
in TBSP1, TBSP2, TBSP3
In this example the first partition will be stored in TBSP1, the second in TBSP2, The third in TBSP3, the fourth in TBSP1 and so on.
Table partitions are named in DB2 - by default PART1 ..PARTn - and all these details can be looked up in the system catalog view SYSCAT.DATAPARTITIONS including the specified partition ranges.
See also http://www-01.ibm.com/support/knowledgecenter/SSEPGG_10.5.0/com.ibm.db2.luw.sql.ref.doc/doc/r0021353.html?cp=SSEPGG_10.5.0%2F2-12-8-27&lang=en
The column used as partitioning key can be looked up in syscat.datapartitionexpression.
There is also a long syntax for creating partitioned tables where partition names can be explizitly specified as well as the tablespace where the partitions will get stored.
For applications partitioned tables look like a single normal table.
Partitions can be detached from a partitioned table. In this case a partition is "disconnected" from the partitioned table and converted to a table without moving the data (or vice versa).
best regards
Michael
After a bit of research I finally figure it out and want to share this information with others, I hope it may come useful to others.
How to see this key values ? => For LUW (Linux/Unix/Windows) you can see the keys in the Table Object Editor or the Object Viewer Script tab. For z/OS there is an Object Viewer tab called "Limit Keys". I've opened issue TDB-885 to create an Object Viewer tab for LUW tables.
A simple query to check this values:
SELECT * FROM SYSCAT.DATAPARTITIONS
WHERE TABSCHEMA = ? AND TABNAME = ?
ORDER BY SEQNO
reference: http://www-01.ibm.com/support/knowledgecenter/SSEPGG_9.5.0/com.ibm.db2.luw.sql.ref.doc/doc/r0021353.html?lang=en
DB2 will create separate Physical Locations for each partition. So each partition will have its own Table-space. When you SELECT on this partitioned Table your SQL may directly go to a single partition or it may span across many depending on how your SQL is. Also, this may allow your SQL to run in parallel i.e. many TS can be accessed concurrently to speed up the SELECT.
I’d like to update some parameters for a table, such as the dist and sort key. In order to do so, I’ve renamed the old version of the table, and recreated the table with the new parameters (these can not be changed once a table has been created).
I need to preserve the id field from the old table, which is an IDENTITY field. If I try the following query however, I get an error:
insert into edw.my_table_new select * from edw.my_table_old;
ERROR: cannot set an identity column to a value [SQL State=0A000]
How can I keep the same id from the old table?
You can't INSERT data setting the IDENTITY columns, but you can load data from S3 using COPY command.
First you will need to create a dump of source table with UNLOAD.
Then simply use COPY with EXPLICIT_IDS parameter as described in Loading default column values:
If an IDENTITY column is included in the column list, the EXPLICIT_IDS
option must also be specified in the COPY command, or the COPY command
will fail. Similarly, if an IDENTITY column is omitted from the column
list, and the EXPLICIT_IDS option is specified, the COPY operation
will fail.
You can explicitly specify the columns, and ignore the identity column:
insert into existing_table (col1, col2) select col1, col2 from another_table;
Use ALTER TABLE APPEND twice, first time with IGNOREEXTRA and the second time with FILLTARGET.
If the target table contains columns that don't exist in the source
table, include FILLTARGET. The command fills the extra columns in the
source table with either the default column value or IDENTITY value,
if one was defined, or NULL.
It moves the columns from one table to another, extremely quickly; took me 4s for 1GB table in dc1.large node.
Appends rows to a target table by moving data from an existing source
table.
...
ALTER TABLE APPEND is usually much faster than a similar CREATE TABLE
AS or INSERT INTO operation because data is moved, not duplicated.
Faster and simpler than UNLOAD + COPY with EXPLICIT_IDS.