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40 строки
844 B
Plaintext
40 строки
844 B
Plaintext
https://www.postgresql.org/docs/current/storage.html
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https://www.postgresql.org/docs/current/storage-page-layout.html
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https://postgrespro.ru/docs/postgrespro/current/storage-page-layout
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each table consists from multiple layers
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each file is no more than 1 Gb
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object layers
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?init?
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zagotovka of main
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used only while "sboy"
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main
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NNN.2
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NNN.1
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NNN
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fsm (free space mem)
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NNN_fsm
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NNN_fsm.1
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vm (visibility map, needed for vacuum optimization)
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NNN_vm
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Each file is a set of pages
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page
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header
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[some free space]
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data
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Buffer cache (caches some pages)
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note
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on index-only scan we can't just use index (need xmin, xmax)
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visibility map allow us to overcome this limitation
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# cmd-line util
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$ oid2name
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pg_total_relation_size(<tblname>)
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pg_relation_size(<tblname>, <layername>)
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pg_indexes_size(<tblname>)
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