Hi,
in case one use 'inherits' relationship to create a hierarchy of
tables, table 'pg_inherits' stores for each table the information of which
is its parent table.
During the evaluation of a query like
select * from Root;
where Root is the 'root' table of our hierarchy, postgreSQL needs to
Also i'd like to answer you if postgresQL has implemented rcursive queries
proposed from SQL99 standard?
If yes, are there any restrictions of the model on your implementation?
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TIP 2: you can get off all lists at once
varchar means 'character varying'. What varies is the length. So a
varchar(1000) with 'foo' in it only takes a few bytes ('foo' plus length
info) instead of 1000 bytes.
Yes i know it, but i have vorgotten to inform you that all the values of
this attribute have really 1000 characthers
Is there any compression or what?
Yes, there is:
http://www.postgresql.org/docs/8.0/interactive/storage-toast.html
thanks, is there any way to increase the limit, upper wich toast strategy
is selected? By defaullt is Block_size/4 = about 2000 Bytes.
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Hi, i found this form of output of explain analyze, watching some old
mails in lists.
test4=# explain analyze select * from patients;
LOG: query: explain analyze select * from patients;
LOG: duration: 0.603887 sec
LOG: QUERY STATISTICS
! system usage stats:
! 0.624269 elapsed 0.458985
Hi,
i have a table:
create table triples(
att0 varchar(1000),
att1 int4,
att2 varchar(20),
att3 varchar(1000)
)
My table has 990 raws.
The (possibly wrong) way, with wich i compute the size of the table is:
att0: 1000 * 1 Byte + 4 = 1004 Bytes
att2: 20 * 1
let me, i have turned enable_seqscan to off, in order to discourage
optimizer to choose seq_scan whenever an idex_scan can be used.
But in this case, why optimizer don't chooses seq_scan (discourage is
different than prevent) ?
At many cases i need only a small fragment of raws to be
If there are many identical values in att0, are you sure a sequential
scan isn't more efficient? Also, are you sure the index isn't working
well? It seems to me since you have the table clustered, it might be
fairly efficient as-is (it would get a huge benefit from the spatial
locality of
Please let me know, if there is any option in postgresql to achieve the
following usage of a b-tree index:
For a relation R(att0, att1) and a btree index on attribute att0
In each insertion of a tuple on table:
- look on index if the value of att0 of new entry does already exist in
index,
