Re: approve VKPts5 unsubscribe pgsql

Hi!

1. I have:
vladimir=> explain SELECT acc.ifs_account_id FROM
vladimir-> ifs_account acc,
vladimir-> ifs_tree_default def,
vladimir-> ifs_account_tree_data atd
vladimir-> WHERE
vladimir-> acc.ifs_status_id = 12
vladimir-> AND atd.ifs_tree_id IN(14,26)
vladimir-> AND def.ifs_tree_default_id IN(587,175)
vladimir-> AND atd.ifs_account_id = acc.ifs_account_id
vladimir-> AND atd.ifs_data_id = def.ifs_data_id;
NOTICE: QUERY PLAN:

Nested Loop (cost=0.00 rows=1 width=16)
-> Seq Scan on ifs_account acc (cost=0.00 rows=0 width=4)
-> Seq Scan (cost=757.02 rows=1 width=12)
(**) -> ??? (cost=757.02 rows=1 width=12)
-> Hash Join (cost=757.02 rows=1 width=12)
-> Seq Scan on ifs_account_tree_data atd (cost=751.76 rows=3 width=8
)
-> Hash (cost=4.07 rows=3 width=4)
-> Index Scan using xpkifs_tree_default, xpkifs_tree_default on
ifs_tree_default def (cost=4.07 rows=3 width=4)

What mean "???" at (**).
There is no index? Or unknown method?

2. Seq Scan - Sequential Scan - this mean FULL TABLE SCAN (DATA SCAN)?

3. I try to play with indeces on this tables
3.1. Setting all btree indeces
explain SELECT acc.ifs_account_id FROM
ifs_account acc,
ifs_tree_default def,
ifs_account_tree_data atd
WHERE
acc.ifs_status_id = 12
AND atd.ifs_tree_id IN(14,26)
AND def.ifs_tree_default_id IN(587,175)
AND atd.ifs_account_id = acc.ifs_account_id
AND atd.ifs_data_id = def.ifs_data_id;

Nested Loop (cost=0.00 rows=1 width=16)
-> Nested Loop (cost=0.00 rows=1 width=12)
-> Seq Scan on ifs_tree_default def (cost=0.00 rows=0 width=4)
-> Seq Scan on ifs_account_tree_data atd (cost=0.00 rows=0 width=8)
-> Seq Scan on ifs_account acc (cost=0.00 rows=0 width=4)

Not optimal way I think

2. I've replace btree indexes on relation
AND atd.ifs_data_id = def.ifs_data_id;
with:
create index itd_hash_data_id on ifs_tree_default USING HASH (ifs_data_id);
create index iatd_hash_data_id on ifs_account_tree_data USING HASH (ifs_data_id);

PS: Can't replace on on ifs_account_id because of PRIMARY KEY (may be
direct Alternative Entry helps me, but is it right way to optimize?)

so:
Nested Loop (cost=0.00 rows=1 width=16)
-> Seq Scan on ifs_account acc (cost=0.00 rows=0 width=4)
-> Seq Scan (cost=10.17 rows=1 width=12)
-> ??? (cost=10.17 rows=1 width=12)
-> Nested Loop (cost=10.17 rows=1 width=12)
-> Index Scan using xpkifs_tree_default, xpkifs_tree_default on ifs_tree_default def (cost=4.07 ows=3 width=4)
-> Index Scan using xif588ifs_account_tree_data on ifs_account_tree_d
ata atd (cost=2.03 rows=3 width=8)

3. I've delete all indexes on
AND atd.ifs_data_id = def.ifs_data_id;

Then I've got:
Nested Loop (cost=0.00 rows=1 width=16)
-> Seq Scan on ifs_account acc (cost=0.00 rows=0 width=4)
-> Seq Scan (cost=757.02 rows=1 width=12)
-> ??? (cost=757.02 rows=1 width=12)
-> Hash Join (cost=757.02 rows=1 width=12)
-> Seq Scan on ifs_account_tree_data atd (cost=751.76 rows=3 width=8
)
-> Hash (cost=4.07 rows=3 width=4)
-> Index Scan using xpkifs_tree_default, xpkifs_tree_default on
ifs_tree_default def (cost=4.07 rows=3 width=4)

Hash Join appears. But there is no indexes, so "Table Scan" appears
(approximately 18000 rows in ifs_account_tree_data)? BAD!?!

So, where is the optimal way?
To make separate queries and use temporary tables to decrease JOINs?

Regards, Alexey V. Meledin
InterForge Developers Group, Saint-Petersburg
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