Re: [GENERAL] Tuning queries on large database

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Valerie Schneider DSI/DEV wrote:

| #---------------------------------------------------------------------------
| # RESOURCE USAGE (except WAL)
| #---------------------------------------------------------------------------
|
| # - Memory -
|
| shared_buffers = 30000          # min 16, at least max_connections*2, 8KB each
| #sort_mem = 1024                # min 64, size in KB
| sort_mem = 5000         # min 64, size in KB
| #vacuum_mem = 8192              # min 1024, size in KB
|
| # - Free Space Map -
|
| #max_fsm_pages = 20000          # min max_fsm_relations*16, 6 bytes each
| #max_fsm_relations = 1000       # min 100, ~50 bytes each
|
| # - Kernel Resource Usage -
|
| #max_files_per_process = 1000   # min 25
| #preload_libraries = ''
|
|
| #---------------------------------------------------------------------------
| # WRITE AHEAD LOG
| #---------------------------------------------------------------------------
|
| # - Settings -
|
| #fsync = true                   # turns forced synchronization on or off
| #wal_sync_method = fsync        # the default varies across platforms:
|                                 # fsync, fdatasync, open_sync, or open_datasync
| #wal_buffers = 8                # min 4, 8KB each
|
| # - Checkpoints -
|
| #checkpoint_segments = 3        # in logfile segments, min 1, 16MB each
| checkpoint_segments = 30        # in logfile segments, min 1, 16MB each
| #checkpoint_timeout = 300       # range 30-3600, in seconds
| #checkpoint_warning = 30        # 0 is off, in seconds
| #commit_delay = 0               # range 0-100000, in microseconds
| #commit_siblings = 5            # range 1-1000
|
|
| #---------------------------------------------------------------------------
| # QUERY TUNING
| #---------------------------------------------------------------------------
|
| # - Planner Method Enabling -
|
| #enable_hashagg = true
| #enable_hashjoin = true
| #enable_indexscan = true
| #enable_mergejoin = true
| #enable_nestloop = true
| enable_seqscan = false
| #enable_sort = true
| #enable_tidscan = true
|
| # - Planner Cost Constants -
|
| #effective_cache_size = 1000    # typically 8KB each
| effective_cache_size = 200000   # typically 8KB each
| #random_page_cost = 4           # units are one sequential page fetch cost
| random_page_cost = 2            # units are one sequential page fetch cost
| #cpu_tuple_cost = 0.01          # (same)
| #cpu_index_tuple_cost = 0.001   # (same)
| #cpu_operator_cost = 0.0025     # (same)
|
| # - Genetic Query Optimizer -
|
| #geqo = true
| #geqo_threshold = 11
| #geqo_effort = 1
| #geqo_generations = 0
| #geqo_pool_size = 0             # default based on tables in statement,
|                                 # range 128-1024
| #geqo_selection_bias = 2.0      # range 1.5-2.0



Your wal_buffers is too small try do bump up your wal_buffers to ~3000,
and see the effects.

why did you disable the sequential_scan (see later) ?

Try also to lower  the cpu_costs:

cpu_tuple_cost = 0.005
cpu_index_tuple_cost = 0.0005   # (same)
cpu_operator_cost = 0.0005     # (same)

this will push the optimizer to choose the index scans.
If not show us the explain with enable_seqscan = false
and with enable_seqscan = true

*Mount also your partition with the noatime parameter*




Regards
Gaeatano Mendola








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