ISQL output of explained plan is shorter by ~ 2 times when query is simplified
by removing one of selected columns from it
--------------------------------------------------------------------------------------------------------------------------
Key: CORE-5061
URL: http://tracker.firebirdsql.org/browse/CORE-5061
Project: Firebird Core
Issue Type: Bug
Components: ISQL
Reporter: Pavel Zotov
Attachments: isql-explained-plan-cut-off-when-query-is-simlified.zip
Consider two queries from attached zip. The only difference between them is:
Q1:
select
char_length(mon$explained_plan)
,(select count(*) from r4)
,(select count(*) from rn)
,(select count(*) from rn)
from mon$statements
Q2:
select
char_length(mon$explained_plan)
,(select count(*) from r4)
,(select count(*) from rn)
--,(select count(*) from rn)
from mon$statements
(i.e. Q2 is simplified: one of columns is excluded from selection).
Q1 has length of mon$explained plan = 64436 and length of ouput in ISQL when
"set explain on" = 64944 (difference ~500 can be explained by number of
occurences ascii_char(13) in output of 'set explain on').
Q2 (which is **simplified** case of Q1) has length of mon$explained plan =
63237 but length of ouput in ISQL when "set explain on" = 33024. Plan in ISQL
looks as:
===
-> Nested Loop Join (anti)
-> Recursion
-> First N Records
-> Window
-> Record Buffer
(record length: ...
===
Checked on WI-V3.0.0.32256.
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