Query performances !?

Hi all,

I'm new to PostgreSQL and I working on some tests. Currently I've loaded a
"moviment" table with ~600K rows (table and index descriptions are below).
I've compiled the 6.5.2 version on SCO Openserver 5.0.4, CPU is P200MMX,
RAM 64Mb, controller SCSI Tekram DC390WUF, 2 x HDD SCSI II Wide 4Gb.

My question is simple, on query below I notice that wasn't used any index.
Only sequential scan. Why ? I expect that the PostgreSQL use at least the
"moviment_index_10" index. And finally, why the costs for the 2 query are
the same ?

Thanks in advance.

Roberto Fichera,
TeknoSOFT.

+-----------------------------------------------------------------------------+
explain select mvm_cdep as "Deposito",
sum(mvm_qtmv) as "Numero Pezzi",
sum(mvm_qtmv*mvm_prez) as "Totale"
from moviment
where mvm_dreg between '1999/07/01'::date and '1999/07/31'::date and
mvm_caus = '006' and
mvm_cdep > 1 and mvm_annc = 1999
group by mvm_cdep;
NOTICE: QUERY PLAN:

Aggregate (cost=42591.91 rows=68 width=12)
-> Group (cost=42591.91 rows=68 width=12)
-> Sort (cost=42591.91 rows=68 width=12)
-> Seq Scan on moviment (cost=42591.91 rows=68 width=12)
+-----------------------------------------------------------------------------+
explain select mvm_cdep as "Deposito",
date_part('month',mvm_dreg) as "Mese",
sum(mvm_qtmv) as "Numero Pezzi",
sum(mvm_qtmv*mvm_prez) as "Totale"
from moviment
where mvm_dreg between '1999/05/01'::date and '1999/08/30'::date and
mvm_caus = '006' and
mvm_cdep > 1 and mvm_annc = 1999
group by mvm_cdep,date_part('month',mvm_dreg);
NOTICE: QUERY PLAN:

Aggregate (cost=42591.91 rows=68 width=12)
-> Group (cost=42591.91 rows=68 width=12)
-> Sort (cost=42591.91 rows=68 width=12)
-> Seq Scan on moviment (cost=42591.91 rows=68 width=12)
+-----------------------------------------------------------------------------+

Table = moviment
+----------------------------------+----------------------------------+-------+
| Field | Type | Length|
+----------------------------------+----------------------------------+-------+
| mvm_annc | float4 | 4 |
| mvm_nupr | float4 | 4 |
| nri_moviment | float4 | 4 |
| mvm_ddoc | date | 4 |
| mvm_seri | char() | 2 |
| mvm_ndoc | float4 | 4 |
| mvm_ccfd | float4 | 4 |
| mvm_dreg | date | 4 |
| mvm_tidc | char() | 1 |
| mvm_cdep | float4 | 4 |
| mvm_cage | char() | 3 |
| mvm_cagz | char() | 3 |
| mvm_cndp | float4 | 4 |
| mvm_cncf | float4 | 4 |
| mvm_caus | char() | 4 |
| mvm_zona | char() | 2 |
| mvm_szon | char() | 3 |
| mvm_fbol | char() | 1 |
| mvm_cart | char() | 15 |
| mvm_comm | char() | 15 |
| mvm_qtmv | float4 | 4 |
| mvm_prez | float4 | 4 |
| mvm_sco1 | float4 | 4 |
| mvm_sco2 | float4 | 4 |
| mvm_sco3 | float4 | 4 |
| mvm_sco4 | float4 | 4 |
| mvm_sco5 | float4 | 4 |
| mvm_impe | char() | 1 |
| mvm_stts | char() | 1 |
| mvm_fili | char() | 5 |
| mvm_rife | char() | 13 |
| mvm_caur | char() | 4 |
| mvm_filc | char() | 15 |
| mvm_sco6 | float4 | 4 |
| mvm_sco7 | float4 | 4 |
| mvm_sco8 | float4 | 4 |
| mvm_pa17 | char() | 1 |
| mvm_pa18 | char() | 1 |
| mvm_cate | char() | 4 |
| mvm_fill | char() | 21 |
| mvm_stat | char() | 1 |
| mvm_ftrs | char() | 1 |
| mvm_datr | date | 4 |
+----------------------------------+----------------------------------+-------+
Indices: moviment_index_0
moviment_index_1
moviment_index_10
moviment_index_2
moviment_index_3

Table = moviment_index_0
+----------------------------------+----------------------------------+-------+
| Field | Type | Length|
+----------------------------------+----------------------------------+-------+
| mvm_annc | float4 | 4 |
| mvm_nupr | float4 | 4 |
| nri_moviment | float4 | 4 |
+----------------------------------+----------------------------------+-------+

Table = moviment_index_1
+----------------------------------+----------------------------------+-------+
| Field | Type | Length|
+----------------------------------+----------------------------------+-------+
| mvm_annc | float4 | 4 |
| mvm_ddoc | date | 4 |
| mvm_seri | char() | 2 |
| mvm_ndoc | float4 | 4 |
+----------------------------------+----------------------------------+-------+

Table = moviment_index_10
+----------------------------------+----------------------------------+-------+
| Field | Type | Length|
+----------------------------------+----------------------------------+-------+
| mvm_annc | float4 | 4 |
| mvm_cdep | float4 | 4 |
| mvm_dreg | date | 4 |
+----------------------------------+----------------------------------+-------+

Table = moviment_index_2
+----------------------------------+----------------------------------+-------+
| Field | Type | Length|
+----------------------------------+----------------------------------+-------+
| mvm_annc | float4 | 4 |
| mvm_cncf | float4 | 4 |
| mvm_ddoc | date | 4 |
+----------------------------------+----------------------------------+-------+

Table = moviment_index_3
+----------------------------------+----------------------------------+-------+
| Field | Type | Length|
+----------------------------------+----------------------------------+-------+
| mvm_annc | float4 | 4 |
| mvm_cdep | float4 | 4 |
| mvm_cart | char() | 15 |
| mvm_dreg | date | 4 |
+----------------------------------+----------------------------------+-------+

Xmeo 4.b9 on Windows 95 4.0 (Pentium)