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PostgreSQL 10 Administration Cookbook - Fourth Edition
book

PostgreSQL 10 Administration Cookbook - Fourth Edition

by Simon Riggs, Gianni Ciolli
May 2018
Intermediate to advanced content levelIntermediate to advanced
576 pages
30h 25m
English
Packt Publishing
Content preview from PostgreSQL 10 Administration Cookbook - Fourth Edition

Function 1 – Estimating the number of rows

The following function estimates the total number of rows using a mathematical procedure called extrapolation. In other words, we take the average number of bytes per row resulting from the last statistics collection, and we apply it to the current table size:

CREATE OR REPLACE FUNCTION estimated_row_count(text) RETURNS bigint LANGUAGE sql AS $$ SELECT (CASE WHEN reltuples > 0 THEN               pg_relation_size($1)*reltuples/(8192*relpages)              ELSE 0              END)::bigint FROM pg_class WHERE oid = $1::regclass; $$;
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Publisher Resources

ISBN: 9781788474924Supplemental Content