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24 lines
937 B
Plaintext
24 lines
937 B
Plaintext
.pgaw:Help.f.t insert end "EXPLAIN" {bold} " This command outputs details about the supplied query. The default output is the computed query cost. The cost value is only meaningful to the optimizer in comparing various query plans. \
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VERBOSE displays the full query plan and cost to your screen, and pretty-prints the plan to the postmaster log file.
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" {} "Synopsis" {bold} "
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" {} "
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EXPLAIN \[ VERBOSE \] query
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" {code} "Usage" {bold} "
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To show a query plan for a simple query:
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" {} "
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postgres=> explain select * from foo;
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NOTICE: QUERY PLAN:
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Seq Scan on foo (cost=0.00 rows=0 width=4)
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EXPLAIN
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" {code} "Notes" {bold} "
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There is only sparse documentation on the optimizer's use of cost information in Postgres. General information on cost estimation for query optimization can be found in database textbooks.
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Refer to the Programmer's Guide in the chapters on indexes and the genetic query optimizer for more \
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information."
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