So I'd like make a query that shows all the datasets from a project, and the number of tables in each one. My problem is with the number of tables.
Here is what I'm stuck with :
SELECT
smt.catalog_name as `Project`,
smt.schema_name as `DataSet`,
( SELECT
COUNT(*)
FROM ***DataSet***.INFORMATION_SCHEMA.TABLES
) as `nbTable`,
smt.creation_time,
smt.location
FROM
INFORMATION_SCHEMA.SCHEMATA smt
ORDER BY DataSet
The view INFORMATION_SCHEMA.SCHEMATA lists all the datasets from the project the query is executed, and the view INFORMATION_SCHEMA.TABLES lists all the tables from a given dataset.
The thing is that the view INFORMATION_SCHEMA.TABLES needs to have the dataset specified like this give the tables informations : dataset.INFORMATION_SCHEMA.TABLES
So what I need is to replace the *** DataSet*** by the one I got from the query itself (smt.schema_name).
I am not sure if I can do it with a sub query, but I don't really know how to manage to do it.
I hope I'm clear enough, thanks in advance if you can help.
You can do this using some procedural language as follows:
CREATE TEMP TABLE table_counts (dataset_id STRING, table_count INT64);
FOR record IN
(
SELECT
catalog_name as project_id,
schema_name as dataset_id
FROM `elzagales.INFORMATION_SCHEMA.SCHEMATA`
)
DO
EXECUTE IMMEDIATE
CONCAT("INSERT table_counts (dataset_id, table_count) SELECT table_schema as dataset_id, count(table_name) from ", record.dataset_id,".INFORMATION_SCHEMA.TABLES GROUP BY dataset_id");
END FOR;
SELECT * FROM table_counts;
This will return something like:
Related
I am getting error when trying to use listagg function.
Query
select
a.user_name,
listagg(a.group_name::text)
within group (order by a.group_name) as group_name
from (
SELECT
usename as user_name,
groname as group_name
FROM
pg_user
join
pg_group
on
pg_user.usesysid = ANY(pg_group.grolist) AND
pg_group.groname in (SELECT DISTINCT pg_group.groname from pg_group)
)a
group by user_name
Error
[Code: 500310, SQL State: XX000] Amazon Invalid operation: One or more of the used functions must be applied on at least one user created tables. Examples of user table only functions are LISTAGG, MEDIAN, PERCENTILE_CONT, etc;
None of the value is null.
Just like there are some functions that can only be run on the leader node there are some that can only be run on compute nodes - listagg() is one of these. If you need to run listagg() on leader data there are a few approaches you can use: (sorry I'm not on a cluster now so cannot test these directly - I saw your question was aging and thought I'd get you started. Grain of salt as I also cannot directly observe your issue but I think I've know what is going on.)
You can use a cursor to save the data from the leader node and use
this as the source for listagg(). A stored procedure can
streamline this. There are examples of this on stackoverflow.
You can make a temp table out of the leader node data and use this
in listagg() but I expect you will need to exit(unload) and
reenter(copy) the cluster to do this.
There just isn't a direct path from leader-node-only results to the compute nodes without some sort of this kind of push-up. Consequence of the large networked cluster architecture of Redshift.
UPDATE
I got some cluster time and there are several unexpected issues with this one. grolist is an array type that isn't generally support cluster wide and the need to user pg_group as source are key ones. So this is going to require #1 AND #2 from above.
The process goes like this:
Define cursor to hold the result of the pg_user / pg_group join select statement
Move cursor results to temp table
Use temp table as source to outer (list_agg()) select
A stored procedure can be written to do #1 and #2 which streamlines things. So you end up with the following SQL:
CREATE OR REPLACE procedure make_user_group()
AS
$$
DECLARE
row record;
BEGIN
create temp table user_group (user_name varchar(256),group_name varchar(256));
for row in SELECT
usename::text as user_name,
groname::text as group_name
FROM
pg_user
join
pg_group
on
pg_user.usesysid = ANY(pg_group.grolist) AND
pg_group.groname in (SELECT DISTINCT pg_group.groname from pg_group)
LOOP
INSERT INTO user_group(user_name,group_name) VALUES (row.user_name,row.group_name);
END LOOP;
END;
$$ LANGUAGE plpgsql;
call make_user_group();
select
user_name,
listagg(group_name::text, ', ')
within group (order by group_name) as group_name
from user_group
group by user_name;
Clearly the stored procedure only needs to be created once but called every time the temp table needs to be created.
I want to achieve result from a table where I ORDER BY column id and I don't want id to be present in the result. I can achieve this using the following query.
SELECT COALESCE (col1, '**')
FROM (select col1, id FROM myDataSet.myTable WHERE col4 = 'some filter' ORDER BY id);
Now, I want to create a RelNode of the above query. As far as I know, in calcite, to perform table scan, there are only two methods scan(String tableName) and scan(Iterable<String> tableNames). Is there a way to scan(RelNode ) ? How to do this ?
The query
select col1, col2, col2 FROM myDataSet.myTable WHERE col4 = 'some filter' ORDER BY id
should also give you the desired result.
If you want to represent the query you have written more directly, you would start by constructing a RelNode for the query in the from clause, starting with a scan of myDataSet.myTable, adding the filter, and the order. Then you can project the specific set of columns you want.
Just simply create a RelNode of inner subquery and create another projection on top of it. Like so.
builder.scan('myTable')
.filter(builder.call(SqlStdOperator.EQUALS, builder.field(col4), builder.literal('some filter') )))
.project(builder.field('col1'), builder.field('id'))
.sort(builder.field('id'))
.project(builder.call(SqlStdOperator.COALESCE(builder.field('col1'), builder.literal('**'))))
.build()
I have two tables (CompletedJobs & ScriptDetails) and using DAX, I want to return distinct Names that appear in CompletedJobs that do not appear in ScriptDetails.
Here is my SQL Query. Works and return values.
Select Distinct CJ.[Name]
From CompletedJobs CJ
Left Join ScriptDetails SD
ON CJ.[Name]=SD.ActivityName
Where SD.ActivityName IS NULL
I started with creating the following DAX query, but just doing this, I get the following error message:
"A table of multiple values was supplied where a single value was expected"
AdhocJobs = DISTINCT(UNION(SELECTCOLUMNS(CompletedJobs,"Name",CompletedJobs[Name]),SELECTCOLUMNS(ScriptDetails,"Name",ScriptDetails[ActivityName])))
How do I create a DAX query that would replicate the SQL query?
Rather than recreate your SQL, there is DAX that already addresses your specific use case. The EXCEPT function returns a table where rows from the LEFT SIDE table do not appear in the RIGHT SIDE table.
EVALUATE
DISTINCT (
EXCEPT (
SUMMARIZE ( CompletedJobs , CompletedJobs [Name]),
SUMMARIZE ( ScriptDetails , ScriptDetails [ActivityName])
)
)
In this case I used SUMMARIZE to reduce each table down to one column, and then wrapped them with EXCEPT to take only the Names from Completed Jobs that aren't ActivityNames in ScriptDetails.
Hope it helps.
From
https://cloud.google.com/bigquery/docs/partitioned-tables:
you can shard tables using a time-based naming approach such as [PREFIX]_YYYYMMDD
This enables me to do:
SELECT count(*) FROM `xxx.xxx.xxx_*`
and query across all the shards. Is there a special notation that queries only the latest shard? For example say I had:
xxx_20180726
xxx_20180801
could I do something along the lines of
SELECT count(*) FROM `xxx.xxx.xxx_{{ latest }}`
to query xxx_20180801?
SINGLE QUERY INSPIRED BY Mikhail Berlyant:
SELECT count(*) as c FROM `XXX.PREFIX_*` WHERE _TABLE_SUFFIX IN ( SELECT
SUBSTR(MAX(table_id), LENGTH('PREFIX_') + 2)
FROM
`XXX.__TABLES_SUMMARY__`
WHERE
table_id LIKE 'PREFIX_%')
If you do care about cost (meaning how many tables will be scaned by your query) - the only way to do so is to do in two steps like below
First query
#standardSQL
SELECT SUBSTR(MAX(table_id), LENGTH('PREFIX') + 1)
FROM `xxx.xxx.__TABLES_SUMMARY__`
WHERE table_id LIKE 'PREFIX%'
Second Query
#standardSQL
SELECT COUNT(*)
FROM `xxx.xxx.PREFIX_*`
WHERE _TABLE_SUFFIX = '<result of first query>'
so, if result of first query is 20180801 so, second query will obviously look like below
#standardSQL
SELECT COUNT(*)
FROM `xxx.xxx.PREFIX_*`
WHERE _TABLE_SUFFIX = '20180801'
If you don't care about cost but rather need just result - you can easily combine above two queries into one - but - again - remember - even though result will be out of last table - cost will be as you query all table that match xxx.xxx.PREFIX_*
Forgot to mention (even though it should be obvious): of course when you have only COUNT(1) in your SELECT - the cost will be 0(zero) for both options - but in reality - most likely you will have something more valuable than just count(1)
I know this is a kind of an old thread but I was surprised why no one offers an answer using Variables.
"Héctor Neri" already mentioned this in the comments but I thought might be better to have an actual answer with a sample code posted.
#standardSQL
DECLARE SHARD_DATE STRING;
SET SHARD_DATE=(
SELECT MAX(REPLACE(table_name,'{TABLE}_',''))
FROM `{PRJ}.{DATASET}.INFORMATION_SCHEMA.TABLES`
WHERE table_name LIKE '{TABLE}_20%'
);
SELECT * FROM `{PRJ}.{DATASET}.{TABLE}_*`
WHERE _TABLE_SUFFIX = SHARD_DATE
Make sure to replace {PRJ}, {DATASET}, and {TABLE} values with your table location.
If you run this on BigQuery Web UI, you will see this message:
WARNING: Could not compute bytes processed estimate for script.
But you can see that variable properly reduce the table scan to the latest partition and does not cause any extra cost after running the script.
class Log:
project = ForeignKey(Project)
msg = CharField(...)
date = DateField(...)
I want to select the four most recent Log entries where each Log entry must have a unique project foreign key. I've tries the solutions on google search but none of them works and the django documentation isn't that very good for lookup..
I tried stuff like:
Log.objects.all().distinct('project')[:4]
Log.objects.values('project').distinct()[:4]
Log.objects.values_list('project').distinct('project')[:4]
But this either return nothing or Log entries of the same project..
Any help would be appreciated!
Queries don't work like that - either in Django's ORM or in the underlying SQL. If you want to get unique IDs, you can only query for the ID. So you'll need to do two queries to get the actual Log entries. Something like:
id_list = Log.objects.order_by('-date').values_list('project_id').distinct()[:4]
entries = Log.objects.filter(id__in=id_list)
Actually, you can get the project_ids in SQL. Assuming that you want the unique project ids for the four projects with the latest log entries, the SQL would look like this:
SELECT project_id, max(log.date) as max_date
FROM logs
GROUP BY project_id
ORDER BY max_date DESC LIMIT 4;
Now, you actually want all of the log information. In PostgreSQL 8.4 and later you can use windowing functions, but that doesn't work on other versions/databases, so I'll do it the more complex way:
SELECT logs.*
FROM logs JOIN (
SELECT project_id, max(log.date) as max_date
FROM logs
GROUP BY project_id
ORDER BY max_date DESC LIMIT 4 ) as latest
ON logs.project_id = latest.project_id
AND logs.date = latest.max_date;
Now, if you have access to windowing functions, it's a bit neater (I think anyway), and certainly faster to execute:
SELECT * FROM (
SELECT logs.field1, logs.field2, logs.field3, logs.date
rank() over ( partition by project_id
order by "date" DESC ) as dateorder
FROM logs ) as logsort
WHERE dateorder = 1
ORDER BY logs.date DESC LIMIT 1;
OK, maybe it's not easier to understand, but take my word for it, it runs worlds faster on a large database.
I'm not entirely sure how that translates to object syntax, though, or even if it does. Also, if you wanted to get other project data, you'd need to join against the projects table.
I know this is an old post, but in Django 2.0, I think you could just use:
Log.objects.values('project').distinct().order_by('project')[:4]
You need two querysets. The good thing is it still results in a single trip to the database (though there is a subquery involved).
latest_ids_per_project = Log.objects.values_list(
'project').annotate(latest=Max('date')).order_by(
'-latest').values_list('project')
log_objects = Log.objects.filter(
id__in=latest_ids_per_project[:4]).order_by('-date')
This looks a bit convoluted, but it actually results in a surprisingly compact query:
SELECT "log"."id",
"log"."project_id",
"log"."msg"
"log"."date"
FROM "log"
WHERE "log"."id" IN
(SELECT U0."id"
FROM "log" U0
GROUP BY U0."project_id"
ORDER BY MAX(U0."date") DESC
LIMIT 4)
ORDER BY "log"."date" DESC