{"id":21768,"date":"2023-05-07T19:52:51","date_gmt":"2023-05-07T16:22:51","guid":{"rendered":"https:\/\/nabfollower.com\/blog\/exploring-the-world-of-databases-cost-estimation-in-single-table-queries-with-postgresql-1gee\/"},"modified":"2023-05-07T19:52:51","modified_gmt":"2023-05-07T16:22:51","slug":"exploring-the-world-of-databases-cost-estimation-in-single-table-queries-with-postgresql-1gee","status":"publish","type":"post","link":"https:\/\/nabfollower.com\/blog\/exploring-the-world-of-databases-cost-estimation-in-single-table-queries-with-postgresql-1gee\/","title":{"rendered":"\u06a9\u0627\u0648\u0634 \u062f\u0631 \u062f\u0646\u06cc\u0627\u06cc \u067e\u0627\u06cc\u06af\u0627\u0647\u200c\u0647\u0627\u06cc \u062f\u0627\u062f\u0647: \u062a\u062e\u0645\u06cc\u0646 \u0647\u0632\u06cc\u0646\u0647 \u062f\u0631 \u062c\u0633\u062a\u0627\u0631\u0647\u0627\u06cc \u062c\u062f\u0648\u0644\u06cc \u0628\u0627 PostgreSQL"},"content":{"rendered":"<div data-article-id=\"1460179\" id=\"article-body\">\n<p>\u0622\u06cc\u0627 \u0622\u0645\u0627\u062f\u0647 \u0647\u0633\u062a\u06cc\u062f \u062a\u0627 \u0639\u0645\u06cc\u0642\u0627\u064b \u062f\u0631 \u062f\u0646\u06cc\u0627\u06cc \u067e\u0627\u06cc\u06af\u0627\u0647 \u062f\u0627\u062f\u0647 \u0647\u0627 \u063a\u0648\u0637\u0647 \u0648\u0631 \u0634\u0648\u06cc\u062f \u0648 \u0639\u0645\u0644\u06a9\u0631\u062f \u062f\u0631\u0648\u0646\u06cc \u067e\u0631\u062f\u0627\u0632\u0634 \u067e\u0631\u0633 \u0648 \u062c\u0648 \u0631\u0627 \u06a9\u0634\u0641 \u06a9\u0646\u06cc\u062f\u061f  \u0628\u06cc\u0627\u06cc\u06cc\u062f \u0628\u0647 \u062f\u0646\u06cc\u0627\u06cc \u067e\u0627\u06cc\u06af\u0627\u0647\u200c\u0647\u0627\u06cc \u062f\u0627\u062f\u0647 \u0633\u0631 \u0628\u0632\u0646\u06cc\u0645 \u0648 \u062f\u0646\u06cc\u0627\u06cc \u0647\u06cc\u062c\u0627\u0646\u200c\u0627\u0646\u06af\u06cc\u0632 \u0628\u0631\u0622\u0648\u0631\u062f \u0647\u0632\u06cc\u0646\u0647 \u0631\u0627 \u062f\u0631 \u062c\u0633\u062a\u0627\u0631\u0647\u0627\u06cc \u062a\u06a9 \u062c\u062f\u0648\u0644\u06cc \u06a9\u0634\u0641 \u06a9\u0646\u06cc\u0645! <\/p>\n<p>\u062f\u0631 \u0627\u06cc\u0646 \u067e\u0633\u062a \u0648\u0628\u0644\u0627\u06af\u060c \u0646\u062d\u0648\u0647 \u0639\u0645\u0644\u06a9\u0631\u062f \u0628\u0647\u06cc\u0646\u0647 \u0633\u0627\u0632\u06cc \u067e\u0631\u0633 \u0648 \u062c\u0648 PostgreSQL \u0628\u0631 \u0627\u0633\u0627\u0633 \u0647\u0632\u06cc\u0646\u0647 \u0631\u0627 \u0628\u0631\u0631\u0633\u06cc \u062e\u0648\u0627\u0647\u06cc\u0645 \u06a9\u0631\u062f.  \u0627\u0645\u0627 \u0646\u06af\u0631\u0627\u0646 \u0646\u0628\u0627\u0634\u06cc\u062f\u060c \u0645\u0627 \u0645\u0641\u0627\u0647\u06cc\u0645 \u067e\u06cc\u0686\u06cc\u062f\u0647 \u067e\u0627\u06cc\u06af\u0627\u0647 \u062f\u0627\u062f\u0647 \u0631\u0627 \u0628\u0627 \u0627\u0633\u062a\u0641\u0627\u062f\u0647 \u0627\u0632 \u0642\u06cc\u0627\u0633 \u0647\u0627\u06cc \u0633\u0631\u06af\u0631\u0645 \u06a9\u0646\u0646\u062f\u0647 \u062a\u062c\u0632\u06cc\u0647 \u0645\u06cc \u06a9\u0646\u06cc\u0645.  \u0647\u0632\u06cc\u0646\u0647 \u0631\u0627 \u0628\u0647 \u0639\u0646\u0648\u0627\u0646 \u0628\u0631\u0686\u0633\u0628 \u0642\u06cc\u0645\u062a \u06cc\u06a9 \u0645\u062d\u0635\u0648\u0644 \u062f\u0631 \u0646\u0638\u0631 \u0628\u06af\u06cc\u0631\u06cc\u062f\u060c \u0627\u06cc\u0646 \u06cc\u06a9 \u0634\u0627\u062e\u0635 \u0645\u0637\u0644\u0642 \u0639\u0645\u0644\u06a9\u0631\u062f \u0646\u06cc\u0633\u062a\u060c \u0628\u0644\u06a9\u0647 \u0627\u0628\u0632\u0627\u0631\u06cc \u0628\u0631\u0627\u06cc \u0645\u0642\u0627\u06cc\u0633\u0647 \u0627\u0631\u0632\u0634 \u0646\u0633\u0628\u06cc \u0639\u0645\u0644\u06cc\u0627\u062a \u0627\u0633\u062a. <\/p>\n<p>\u0647\u0632\u06cc\u0646\u0647 \u0647\u0627 \u0628\u0627 \u062a\u0648\u0627\u0628\u0639 \u062a\u0639\u0631\u06cc\u0641 \u0634\u062f\u0647 \u062f\u0631 costize.c \u062a\u062e\u0645\u06cc\u0646 \u0632\u062f\u0647 \u0645\u06cc \u0634\u0648\u0646\u062f \u0648 \u062a\u0645\u0627\u0645 \u0639\u0645\u0644\u06cc\u0627\u062a \u0627\u062c\u0631\u0627 \u0634\u062f\u0647 \u062a\u0648\u0633\u0637 \u0645\u062c\u0631\u06cc \u062f\u0627\u0631\u0627\u06cc \u062a\u0648\u0627\u0628\u0639 \u0647\u0632\u06cc\u0646\u0647 \u0645\u0631\u0628\u0648\u0637\u0647 \u0647\u0633\u062a\u0646\u062f.  \u0628\u0647 \u0639\u0646\u0648\u0627\u0646 \u0645\u062b\u0627\u0644\u060c \u0647\u0632\u06cc\u0646\u0647 \u0647\u0627\u06cc \u0627\u0633\u06a9\u0646 \u0647\u0627\u06cc \u0645\u062a\u0648\u0627\u0644\u06cc \u0648 \u0627\u0633\u06a9\u0646 \u0647\u0627\u06cc \u0634\u0627\u062e\u0635 \u0628\u0647 \u062a\u0631\u062a\u06cc\u0628 \u062a\u0648\u0633\u0637 cost_seqscan() \u0648 cost_index() \u0628\u0631\u0622\u0648\u0631\u062f \u0645\u06cc \u0634\u0648\u0646\u062f.  \u062f\u0631 PostgreSQL \u0633\u0647 \u0646\u0648\u0639 \u0647\u0632\u06cc\u0646\u0647 \u0648\u062c\u0648\u062f \u062f\u0627\u0631\u062f: \u0631\u0627\u0647 \u0627\u0646\u062f\u0627\u0632\u06cc\u060c \u0627\u062c\u0631\u0627 \u0648 \u06a9\u0644\u060c \u06a9\u0647 \u0647\u0632\u06cc\u0646\u0647 \u06a9\u0644 \u0645\u062c\u0645\u0648\u0639 \u0647\u0632\u06cc\u0646\u0647 \u0647\u0627\u06cc \u0631\u0627\u0647 \u0627\u0646\u062f\u0627\u0632\u06cc \u0648 \u0627\u062c\u0631\u0627 \u0627\u0633\u062a.<\/p>\n<p>\u0647\u0632\u06cc\u0646\u0647 \u0631\u0627\u0647 \u0627\u0646\u062f\u0627\u0632\u06cc \u0647\u0632\u06cc\u0646\u0647 \u0627\u06cc \u0627\u0633\u062a \u06a9\u0647 \u0642\u0628\u0644 \u0627\u0632 \u0648\u0627\u06a9\u0634\u06cc \u0627\u0648\u0644\u06cc\u0646 \u062a\u0627\u067e\u0644 \u0635\u0631\u0641 \u0634\u062f\u0647 \u0627\u0633\u062a.  \u0622\u0646 \u0631\u0627 \u0645\u0627\u0646\u0646\u062f \u0647\u0632\u06cc\u0646\u0647 \u0644\u0628\u0627\u0633 \u067e\u0648\u0634\u06cc\u062f\u0646 \u0648 \u0622\u0645\u0627\u062f\u0647 \u0634\u062f\u0646 \u0642\u0628\u0644 \u0627\u0632 \u062a\u0631\u06a9 \u062e\u0627\u0646\u0647 \u062e\u0648\u062f \u062a\u0635\u0648\u0631 \u06a9\u0646\u06cc\u062f.  \u0627\u0632 \u0633\u0648\u06cc \u062f\u06cc\u06af\u0631\u060c \u0647\u0632\u06cc\u0646\u0647 \u0627\u062c\u0631\u0627\u060c \u0647\u0632\u06cc\u0646\u0647 \u0648\u0627\u06a9\u0634\u06cc \u062a\u0645\u0627\u0645 \u062a\u0627\u067e\u0644 \u0647\u0627 \u06cc\u0627 \u06a9\u0627\u0631 \u0648\u0627\u0642\u0639\u06cc \u0627\u0646\u062c\u0627\u0645 \u0634\u062f\u0647 \u0628\u0631\u0627\u06cc \u0631\u0633\u06cc\u062f\u0646 \u0628\u0647 \u0646\u062a\u06cc\u062c\u0647 \u0627\u0633\u062a.  \u0627\u06cc\u0646 \u0645\u0627\u0646\u0646\u062f \u0627\u0646\u0631\u0698\u06cc \u0627\u0633\u062a \u06a9\u0647 \u067e\u0633 \u0627\u0632 \u0622\u0645\u0627\u062f\u0647 \u0634\u062f\u0646 \u0628\u0631\u0627\u06cc \u0633\u0641\u0631 \u0628\u0647 \u0645\u0642\u0635\u062f\u06cc \u0635\u0631\u0641 \u0645\u06cc \u06a9\u0646\u06cc\u062f. <\/p>\n<p>\u062f\u0633\u062a\u0648\u0631 EXPLAIN \u0647\u0631 \u062f\u0648 \u0647\u0632\u06cc\u0646\u0647 \u0631\u0627\u0647 \u0627\u0646\u062f\u0627\u0632\u06cc \u0648 \u06a9\u0644 \u0647\u0632\u06cc\u0646\u0647 \u0647\u0627 \u0631\u0627 \u062f\u0631 \u0647\u0631 \u0639\u0645\u0644\u06cc\u0627\u062a \u0646\u0634\u0627\u0646 \u0645\u06cc \u062f\u0647\u062f.  \u0645\u062b\u0644\u0627 \u0648\u0642\u062a\u06cc \u0645\u06cc \u062f\u0648\u06cc\u062f <code>EXPLAIN SELECT * FROM tbl;<\/code>\u060c \u0628\u062e\u0634 \u0647\u0632\u06cc\u0646\u0647 \u062f\u0648 \u0645\u0642\u062f\u0627\u0631 0.00 \u0648 145.00 \u0631\u0627 \u0646\u0645\u0627\u06cc\u0634 \u0645\u06cc \u062f\u0647\u062f.  \u062f\u0631 \u0627\u06cc\u0646\u062c\u0627 \u0647\u0632\u06cc\u0646\u0647 \u0631\u0627\u0647 \u0627\u0646\u062f\u0627\u0632\u06cc \u0648 \u06a9\u0644 \u0647\u0632\u06cc\u0646\u0647 \u0647\u0627 \u0628\u0647 \u062a\u0631\u062a\u06cc\u0628 0.00 \u0648 145.00 \u0627\u0633\u062a.<\/p>\n<p>\u0627\u06a9\u0646\u0648\u0646\u060c \u0628\u06cc\u0627\u06cc\u06cc\u062f \u0646\u062d\u0648\u0647 \u062a\u062e\u0645\u06cc\u0646 \u0639\u0645\u0644\u06cc\u0627\u062a \u0627\u0633\u06a9\u0646 \u0645\u062a\u0648\u0627\u0644\u06cc\u060c \u0627\u0633\u06a9\u0646 \u0641\u0647\u0631\u0633\u062a \u0648 \u0645\u0631\u062a\u0628\u200c\u0633\u0627\u0632\u06cc \u0631\u0627 \u0628\u0627 \u062c\u0632\u0626\u06cc\u0627\u062a \u0628\u0631\u0631\u0633\u06cc \u06a9\u0646\u06cc\u0645.  \u0645\u0627 \u0627\u0632 \u06cc\u06a9 \u062c\u062f\u0648\u0644 \u062e\u0627\u0635 \u0648 \u06cc\u06a9 \u0634\u0627\u062e\u0635 \u0628\u0631\u0627\u06cc \u0646\u0634\u0627\u0646 \u062f\u0627\u062f\u0646 \u0646\u062d\u0648\u0647 \u0639\u0645\u0644\u06a9\u0631\u062f \u0627\u06cc\u0646 \u0639\u0645\u0644\u06cc\u0627\u062a \u0627\u0633\u062a\u0641\u0627\u062f\u0647 \u062e\u0648\u0627\u0647\u06cc\u0645 \u06a9\u0631\u062f.<\/p>\n<p>\u0628\u0647 \u0639\u0646\u0648\u0627\u0646 \u0645\u062b\u0627\u0644\u060c \u0647\u0632\u06cc\u0646\u0647 \u0627\u0633\u06a9\u0646 \u0645\u062a\u0648\u0627\u0644\u06cc \u062a\u0648\u0633\u0637 \u062a\u0627\u0628\u0639 cost_seqscan() \u062a\u062e\u0645\u06cc\u0646 \u0632\u062f\u0647 \u0645\u06cc \u0634\u0648\u062f.  \u0628\u06cc\u0627\u06cc\u06cc\u062f \u0646\u062d\u0648\u0647 \u062a\u062e\u0645\u06cc\u0646 \u0647\u0632\u06cc\u0646\u0647 \u0627\u0633\u06a9\u0646 \u0645\u062a\u0648\u0627\u0644\u06cc \u062f\u0631\u062e\u0648\u0627\u0633\u062a \u0632\u06cc\u0631 \u0631\u0627 \u0628\u0631\u0631\u0633\u06cc \u06a9\u0646\u06cc\u0645: <code>SELECT * FROM tbl WHERE id &lt; 8000;<\/code>. <\/p>\n<p>\u062f\u0631 \u0627\u0633\u06a9\u0646 \u0645\u062a\u0648\u0627\u0644\u06cc\u060c \u0647\u0632\u06cc\u0646\u0647 \u0631\u0627\u0647 \u0627\u0646\u062f\u0627\u0632\u06cc \u0628\u0631\u0627\u0628\u0631 \u0628\u0627 0 \u0627\u0633\u062a \u0648 \u0647\u0632\u06cc\u0646\u0647 \u0627\u062c\u0631\u0627 \u0628\u0627 \u0645\u0639\u0627\u062f\u0644\u0647 \u062a\u0639\u0631\u06cc\u0641 \u0645\u06cc \u0634\u0648\u062f:<\/p>\n<p>\u0647\u0632\u06cc\u0646\u0647 \u0627\u062c\u0631\u0627 = (cpu_tuple_cost + cpu_operator_cost) \u00d7 Ntuple + seq_page_cost \u00d7 Npage,<\/p>\n<p>\u062c\u0627\u06cc\u06cc \u06a9\u0647 <code>seq_page_cost<\/code>\u060c <code>cpu_tuple_cost<\/code>\u060c \u0648 <code>cpu_operator_cost<\/code> \u062f\u0631 \u062a\u0646\u0638\u06cc\u0645 \u0634\u062f\u0647 \u0627\u0646\u062f <code>postgresql.conf<\/code> \u0641\u0627\u06cc\u0644\u060c \u0648 \u0645\u0642\u0627\u062f\u06cc\u0631 \u067e\u06cc\u0634 \u0641\u0631\u0636 \u0628\u0647 \u062a\u0631\u062a\u06cc\u0628 1.0\u060c 0.01 \u0648 0.0025 \u0647\u0633\u062a\u0646\u062f. <code>Ntuple<\/code> \u0648 <code>Npage<\/code> \u0628\u0647 \u062a\u0631\u062a\u06cc\u0628 \u062a\u0639\u062f\u0627\u062f \u062a\u0627\u067e\u0644 \u0647\u0627 \u0648 \u0635\u0641\u062d\u0627\u062a \u062c\u062f\u0648\u0644 \u0631\u0627 \u0646\u0634\u0627\u0646 \u0645\u06cc \u062f\u0647\u062f. <\/p>\n<p>\u0645\u0627 \u0645\u06cc \u062a\u0648\u0627\u0646\u06cc\u0645 \u0645\u0642\u0627\u062f\u06cc\u0631 \u0631\u0627 \u0628\u062f\u0633\u062a \u0622\u0648\u0631\u06cc\u0645 <code>Ntuple<\/code> \u0648 <code>Npage<\/code> \u0628\u0627 \u0627\u0633\u062a\u0641\u0627\u062f\u0647 \u0627\u0632 \u067e\u0631\u0633 \u0648 \u062c\u0648 \u0632\u06cc\u0631: <code>SELECT relpages, reltuples FROM pg_class WHERE relname=\"tbl\";<\/code>.  \u0628\u0631\u0627\u06cc \u062c\u062f\u0648\u0644 \u0645\u062b\u0627\u0644 \u0645\u0627\u060c \u062e\u0631\u0648\u062c\u06cc \u0627\u06cc\u0646 \u0627\u0633\u062a:<\/p>\n<div class=\"table-wrapper-paragraph\">\n<table>\n<thead>\n<tr>\n<th>\u062a\u06a9\u0631\u0627\u0631\u0647\u0627<\/th>\n<th>\u062f\u0648\u0628\u0627\u0631\u0647 \u0686\u0646\u062f \u0646\u0641\u0631\u0647<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>45<\/td>\n<td>10000<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>\u0628\u0646\u0627\u0628\u0631\u0627\u06cc\u0646 \u0647\u0632\u06cc\u0646\u0647 \u0627\u062c\u0631\u0627 \u0631\u0627 \u0645\u06cc \u062a\u0648\u0627\u0646 \u0628\u0647 \u0635\u0648\u0631\u062a \u0632\u06cc\u0631 \u0645\u062d\u0627\u0633\u0628\u0647 \u06a9\u0631\u062f:<\/p>\n<p>\u0647\u0632\u06cc\u0646\u0647 \u0627\u062c\u0631\u0627 = (0.01 + 0.0025) \u00d7 10000 + 1.0 \u00d7 45 = 170.0.<\/p>\n<p>\u0648 \u0647\u0632\u06cc\u0646\u0647 \u06a9\u0644 \u0645\u062c\u0645\u0648\u0639 \u0647\u0632\u06cc\u0646\u0647 \u0647\u0627\u06cc \u0631\u0627\u0647 \u0627\u0646\u062f\u0627\u0632\u06cc \u0648 \u0627\u062c\u0631\u0627 \u0627\u0633\u062a:<\/p>\n<p>\u0647\u0632\u06cc\u0646\u0647 \u06a9\u0644 = 0.0 + 170.0 = 170.<\/p>\n<p>\u0627\u06af\u0631 \u0634\u0645\u0627 \u0627\u062c\u0631\u0627 \u06a9\u0646\u06cc\u062f <code>EXPLAIN<\/code> \u062f\u0633\u062a\u0648\u0631 \u0628\u0631\u0627\u06cc \u06a9\u0648\u0626\u0631\u06cc \u0628\u0627\u0644\u0627\u060c \u062e\u0631\u0648\u062c\u06cc \u0632\u06cc\u0631 \u0631\u0627 \u062e\u0648\u0627\u0647\u06cc\u062f \u062f\u06cc\u062f:<\/p>\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_84 counter-hierarchy ez-toc-counter-rtl ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">\u0641\u0647\u0631\u0633\u062a \u0645\u0637\u0627\u0644\u0628<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/nabfollower.com\/blog\/exploring-the-world-of-databases-cost-estimation-in-single-table-queries-with-postgresql-1gee\/#QUERY_PLAN\" >QUERY PLAN<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/nabfollower.com\/blog\/exploring-the-world-of-databases-cost-estimation-in-single-table-queries-with-postgresql-1gee\/#QUERY_PLAN-2\" >QUERY PLAN<\/a><\/li><\/ul><\/nav><\/div>\n<h2><span class=\"ez-toc-section\" id=\"QUERY_PLAN\"><\/span>\n<p>  QUERY PLAN<br \/>\n<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Seq Scan \u062f\u0631 tbl (\u0647\u0632\u06cc\u0646\u0647 = 0.00.. 170.00 \u0631\u062f\u06cc\u0641 = 8000 \u0639\u0631\u0636 = 8)<br \/>\u0641\u06cc\u0644\u062a\u0631: (id < 8000)<br \/>(2 \u0631\u062f\u06cc\u0641)<\/p>\n<p>\u062d\u0627\u0644\u0627 \u0628\u06cc\u0627\u06cc\u06cc\u062f \u0628\u0647 \u062a\u062e\u0645\u06cc\u0646 \u0647\u0632\u06cc\u0646\u0647 \u0627\u0633\u06a9\u0646 \u0634\u0627\u062e\u0635 \u0628\u0631\u0648\u06cc\u0645.  \u0627\u0633\u06a9\u0646 \u0641\u0647\u0631\u0633\u062a \u06a9\u0627\u0631\u0622\u0645\u062f\u062a\u0631 \u0627\u0632 \u0627\u0633\u06a9\u0646 \u0645\u062a\u0648\u0627\u0644\u06cc \u0627\u0633\u062a \u0632\u06cc\u0631\u0627 \u0628\u0647 \u062c\u0627\u06cc \u0627\u0633\u06a9\u0646 \u06a9\u0644 \u062c\u062f\u0648\u0644\u060c \u0641\u0642\u0637 \u0628\u0647 \u0635\u0641\u062d\u0627\u062a \u062f\u0627\u062f\u0647 \u0645\u0648\u0631\u062f \u0646\u06cc\u0627\u0632 \u062f\u0633\u062a\u0631\u0633\u06cc \u062f\u0627\u0631\u062f.  \u0647\u0632\u06cc\u0646\u0647 \u0627\u0633\u06a9\u0646 \u0634\u0627\u062e\u0635 \u062a\u0648\u0633\u0637 \u062a\u0627\u0628\u0639 cost_index() \u062a\u062e\u0645\u06cc\u0646 \u0632\u062f\u0647 \u0645\u06cc \u0634\u0648\u062f.  \u0628\u06cc\u0627\u06cc\u06cc\u062f \u0627\u0632 \u0647\u0645\u0627\u0646 \u062c\u062f\u0648\u0644 \u0627\u0633\u062a\u0641\u0627\u062f\u0647 \u06a9\u0646\u06cc\u0645 <code>tbl<\/code> \u0648 \u06cc\u06a9 \u0634\u0627\u062e\u0635 \u062f\u0631 <code>id<\/code> \u0633\u062a\u0648\u0646\u06cc \u0628\u0631\u0627\u06cc \u0646\u0634\u0627\u0646 \u062f\u0627\u062f\u0646 \u0686\u06af\u0648\u0646\u06af\u06cc \u0628\u0631\u0622\u0648\u0631\u062f \u0647\u0632\u06cc\u0646\u0647 \u0627\u0633\u06a9\u0646 \u0634\u0627\u062e\u0635 \u0628\u0631\u0627\u06cc \u067e\u0631\u0633 \u0648 \u062c\u0648 <code>SELECT * FROM tbl WHERE id &lt; 8000;<\/code>.<\/p>\n<p>\u0647\u0632\u06cc\u0646\u0647 \u0634\u0631\u0648\u0639 \u06cc\u06a9 \u0627\u0633\u06a9\u0646 \u0634\u0627\u062e\u0635 \u0628\u0627 \u0647\u0632\u06cc\u0646\u0647 \u0627\u0633\u06a9\u0646 \u0634\u0627\u062e\u0635 \u0628\u0631\u0627\u06cc \u06cc\u0627\u0641\u062a\u0646 \u0646\u0642\u0637\u0647 \u0634\u0631\u0648\u0639 \u062a\u0639\u0631\u06cc\u0641 \u0645\u06cc \u0634\u0648\u062f.  \u0627\u06cc\u0646 \u0647\u0632\u06cc\u0646\u0647 \u0628\u0627 \u0647\u0632\u06cc\u0646\u0647 \u062f\u0633\u062a\u0631\u0633\u06cc \u0628\u0647 \u06cc\u06a9 \u0635\u0641\u062d\u0647 \u0641\u0647\u0631\u0633\u062a \u0648\u0627\u062d\u062f \u062a\u062e\u0645\u06cc\u0646 \u0632\u062f\u0647 \u0645\u06cc \u0634\u0648\u062f \u06a9\u0647 \u062a\u0648\u0633\u0637 \u0622\u0646 \u062a\u0639\u06cc\u06cc\u0646 \u0645\u06cc \u0634\u0648\u062f <code>random_page_cost<\/code> \u062a\u0646\u0638\u06cc\u0645 \u062f\u0631 <code>postgresql.conf<\/code> \u0641\u0627\u06cc\u0644.  \u0647\u0632\u06cc\u0646\u0647 \u0627\u062c\u0631\u0627\u06cc \u0627\u0633\u06a9\u0646 \u0646\u0645\u0627\u06cc\u0647\u060c \u0647\u0632\u06cc\u0646\u0647 \u0648\u0627\u06a9\u0634\u06cc \u062a\u0645\u0627\u0645 \u062a\u0627\u067e\u0644 \u0647\u0627\u06cc \u0645\u0646\u0637\u0628\u0642 \u0627\u0633\u062a\u060c \u06a9\u0647 \u0645\u0634\u0627\u0628\u0647 \u0647\u0632\u06cc\u0646\u0647 \u0627\u0633\u06a9\u0646 \u0645\u062a\u0648\u0627\u0644\u06cc \u0627\u0633\u062a\u060c \u0627\u0645\u0627 \u062f\u0631 \u0636\u0631\u06cc\u0628 \u0627\u0646\u062a\u062e\u0627\u0628 \u0634\u0627\u062e\u0635 \u0636\u0631\u0628 \u0645\u06cc \u0634\u0648\u062f\u060c \u06a9\u0647 \u06a9\u0633\u0631\u06cc \u0627\u0632 \u0631\u062f\u06cc\u0641 \u0647\u0627\u06cc \u062c\u062f\u0648\u0644 \u0627\u0633\u062a \u06a9\u0647 \u0634\u0631\u0627\u06cc\u0637 \u067e\u0631\u0633 \u0648 \u062c\u0648 \u0631\u0627 \u0628\u0631\u0622\u0648\u0631\u062f\u0647 \u0645\u06cc \u06a9\u0646\u062f. .<\/p>\n<p>\u0636\u0631\u06cc\u0628 \u0627\u0646\u062a\u062e\u0627\u0628 \u06cc\u06a9 \u0634\u0627\u062e\u0635 \u062a\u0648\u0633\u0637 \u0628\u0631\u0646\u0627\u0645\u0647 \u0631\u06cc\u0632 \u0628\u0631 \u0627\u0633\u0627\u0633 \u0622\u0645\u0627\u0631 \u062c\u0645\u0639 \u0622\u0648\u0631\u06cc \u0634\u062f\u0647 \u062a\u0648\u0633\u0637 \u0633\u0627\u0632\u0645\u0627\u0646 \u0628\u0631\u0622\u0648\u0631\u062f \u0645\u06cc \u0634\u0648\u062f <code>ANALYZE<\/code> \u0641\u0631\u0645\u0627\u0646  \u0628\u0631\u0627\u06cc \u067e\u0631\u0633 \u0648 \u062c\u0648\u06cc \u0645\u062b\u0627\u0644 \u0645\u0627\u060c \u0628\u06cc\u0627\u06cc\u06cc\u062f \u0641\u0631\u0636 \u06a9\u0646\u06cc\u0645 \u06a9\u0647 \u0636\u0631\u06cc\u0628 \u0627\u0646\u062a\u062e\u0627\u0628 0.8 \u0627\u0633\u062a\u060c \u0628\u0647 \u0627\u06cc\u0646 \u0645\u0639\u0646\u06cc \u06a9\u0647 80\u066a \u0627\u0632 \u0631\u062f\u06cc\u0641 \u0647\u0627 \u0634\u0631\u0637 \u0631\u0627 \u0628\u0631\u0622\u0648\u0631\u062f\u0647 \u0645\u06cc \u06a9\u0646\u0646\u062f.<\/p>\n<p>\u0647\u0632\u06cc\u0646\u0647 \u0627\u0633\u06a9\u0646 \u0634\u0627\u062e\u0635 \u0631\u0627 \u0645\u06cc \u062a\u0648\u0627\u0646 \u0628\u0647 \u0635\u0648\u0631\u062a \u0632\u06cc\u0631 \u0645\u062d\u0627\u0633\u0628\u0647 \u06a9\u0631\u062f:<\/p>\n<p>\u0647\u0632\u06cc\u0646\u0647 \u0631\u0627\u0647 \u0627\u0646\u062f\u0627\u0632\u06cc = random_page_cost \u00d7 1 = 4.0 (\u0628\u0627 \u0641\u0631\u0636 \u062a\u0635\u0627\u062f\u0641\u06cc_page_cost = 4.0)<br \/>\u0647\u0632\u06cc\u0646\u0647 \u0627\u062c\u0631\u0627 = (cpu_tuple_cost + cpu_operator_cost) \u00d7 Ntuple \u00d7 \u0627\u0646\u062a\u062e\u0627\u0628\u06cc + index_page_cost \u00d7 Nindex<br \/>= (0.01 + 0.0025) \u00d7 10000 \u00d7 0.8 + 0.2 \u00d7 45<br \/>= 82.0<br \/>\u0647\u0632\u06cc\u0646\u0647 \u06a9\u0644 = \u0647\u0632\u06cc\u0646\u0647 \u0631\u0627\u0647 \u0627\u0646\u062f\u0627\u0632\u06cc + \u0647\u0632\u06cc\u0646\u0647 \u0627\u062c\u0631\u0627 = 86.0<\/p>\n<p>\u0627\u06af\u0631 \u0627\u062c\u0631\u0627 \u06a9\u0646\u06cc\u062f <code>EXPLAIN<\/code> \u062f\u0633\u062a\u0648\u0631 \u0628\u0631\u0627\u06cc \u06a9\u0648\u0626\u0631\u06cc \u0628\u0627\u0644\u0627\u060c \u062e\u0631\u0648\u062c\u06cc \u0632\u06cc\u0631 \u0631\u0627 \u062e\u0648\u0627\u0647\u06cc\u062f \u062f\u06cc\u062f:<\/p>\n<h2><span class=\"ez-toc-section\" id=\"QUERY_PLAN-2\"><\/span>\n<p>  QUERY PLAN<br \/>\n<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>\u0627\u0633\u06a9\u0646 \u0641\u0647\u0631\u0633\u062a \u0628\u0627 \u0627\u0633\u062a\u0641\u0627\u062f\u0647 \u0627\u0632 idx_tbl_id \u062f\u0631 tbl (\u0647\u0632\u06cc\u0646\u0647=4.00..86.00 \u0631\u062f\u06cc\u0641=8000 \u0639\u0631\u0636=8)<br \/>\u0648\u0636\u0639\u06cc\u062a \u0634\u0627\u062e\u0635: (id < 8000)<br \/>(2 \u0631\u062f\u06cc\u0641)<\/p>\n<p>\u0645\u06cc \u0628\u06cc\u0646\u06cc\u062f \u06a9\u0647 \u0647\u0632\u06cc\u0646\u0647 \u0627\u0633\u06a9\u0646 \u0634\u0627\u062e\u0635 \u06a9\u0645\u062a\u0631 \u0627\u0632 \u0627\u0633\u06a9\u0646 \u0645\u062a\u0648\u0627\u0644\u06cc \u0627\u0633\u062a\u060c \u06a9\u0647 \u0646\u0634\u0627\u0646 \u0645\u06cc \u062f\u0647\u062f \u0627\u0633\u06a9\u0646 \u0634\u0627\u062e\u0635 \u0628\u0631\u0627\u06cc \u0627\u06cc\u0646 \u067e\u0631\u0633 \u0648 \u062c\u0648 \u062e\u0627\u0635 \u06a9\u0627\u0631\u0622\u0645\u062f\u062a\u0631 \u0627\u0633\u062a.<\/p>\n<p>\u062f\u0631 \u0646\u0647\u0627\u06cc\u062a\u060c \u0627\u062c\u0627\u0632\u0647 \u062f\u0647\u06cc\u062f \u0628\u0647 \u0637\u0648\u0631 \u062e\u0644\u0627\u0635\u0647 \u062f\u0631 \u0645\u0648\u0631\u062f \u0686\u06af\u0648\u0646\u06af\u06cc \u0628\u0631\u0622\u0648\u0631\u062f \u0647\u0632\u06cc\u0646\u0647 \u0639\u0645\u0644\u06cc\u0627\u062a \u0645\u0631\u062a\u0628 \u0633\u0627\u0632\u06cc \u0628\u062d\u062b \u06a9\u0646\u06cc\u0645.  \u0645\u0631\u062a\u0628 \u0633\u0627\u0632\u06cc \u06cc\u06a9 \u0639\u0645\u0644\u06cc\u0627\u062a \u06af\u0631\u0627\u0646 \u0642\u06cc\u0645\u062a \u0627\u0633\u062a \u06a9\u0647 \u0628\u0647 CPU \u0648 \u0645\u0646\u0627\u0628\u0639 I\/O \u0632\u06cc\u0627\u062f\u06cc \u0646\u06cc\u0627\u0632 \u062f\u0627\u0631\u062f.  \u0647\u0632\u06cc\u0646\u0647 \u0639\u0645\u0644\u06cc\u0627\u062a \u0645\u0631\u062a\u0628 \u0633\u0627\u0632\u06cc \u062a\u0648\u0633\u0637 \u062a\u0627\u0628\u0639 cost_sort() \u062a\u062e\u0645\u06cc\u0646 \u0632\u062f\u0647 \u0645\u06cc \u0634\u0648\u062f \u06a9\u0647 \u0627\u0646\u062f\u0627\u0632\u0647 \u062f\u0627\u062f\u0647 \u0647\u0627\u06cc\u06cc \u06a9\u0647 \u0628\u0627\u06cc\u062f \u0645\u0631\u062a\u0628 \u0634\u0648\u0646\u062f\u060c \u062d\u0627\u0641\u0638\u0647 \u0645\u0648\u062c\u0648\u062f \u0648 \u0647\u0632\u06cc\u0646\u0647 \u0646\u0648\u0634\u062a\u0646 \u0648 \u062e\u0648\u0627\u0646\u062f\u0646 \u062f\u0627\u062f\u0647 \u0647\u0627 \u0628\u0647 \u062f\u06cc\u0633\u06a9 \u0648 \u0627\u0632 \u062f\u06cc\u0633\u06a9 \u0631\u0627 \u062f\u0631 \u0646\u0638\u0631 \u0645\u06cc \u06af\u06cc\u0631\u062f.<\/p>\n<p>\u062f\u0631 \u0646\u062a\u06cc\u062c\u0647\u060c 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