Re: cannot use multicolumn index

-postgres version -> 8.4.4
-os -> redhat 5.6
-specs ->24 cores, 96GB ram, shared_buffers=32 GB
-postgresql.conf -> i havent made any changes as far as the query tuning
parameters are concerned.
#------------------------------------------------------------------------------
# QUERY TUNING
#------------------------------------------------------------------------------

# - Planner Method Configuration -

#enable_bitmapscan = on
#enable_hashagg = on
#enable_hashjoin = on
#enable_indexscan = on
#enable_mergejoin = on
#enable_nestloop = on
#enable_seqscan = on
#enable_sort = on
#enable_tidscan = on

# - Planner Cost Constants -

#seq_page_cost = 1.0 # measured on an arbitrary scale
#random_page_cost = 4.0 # same scale as above
#cpu_tuple_cost = 0.01 # same scale as above
#cpu_index_tuple_cost = 0.005 # same scale as above
#cpu_operator_cost = 0.0025 # same scale as above
effective_cache_size = 50GB

# - Genetic Query Optimizer -

#geqo = on
#geqo_threshold = 12
#geqo_effort = 5 # range 1-10
#geqo_pool_size = 0 # selects default based on effort
#geqo_generations = 0 # selects default based on effort
#geqo_selection_bias = 2.0 # range 1.5-2.0

# - Other Planner Options -

#default_statistics_target = 100 # range 1-10000
#constraint_exclusion = partition # on, off, or partition
#cursor_tuple_fraction = 0.1 # range 0.0-1.0
#from_collapse_limit = 8
#join_collapse_limit = 8 # 1 disables collapsing of explicit
# JOIN clauses
--------------------------------------------------------------------------------------------------------------

if any other parameters are relative to my question pls tell me which you
want and i can post them (i can post the whole postgresql.conf if it's
helpful). my shared buffers ar

my question apart from the specific example, is a little more general. so,
is it normal to expect such an index to be used? can i write the query in
another form so as to use this index? is it for example that the conditions
are '>' and not '=' a factor why the index is not used?

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