|From:||Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>|
|To:||Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>|
|Cc:||robertmhaas(at)gmail(dot)com, PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org>|
|Subject:||Re: BUG: pg_stat_statements query normalization issues with combined queries|
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> Yes. I'll try to put together a patch and submit it to the next CF.
Here it is. I'll add this to the next CF.
This patch fixes the handling of compound/combined queries by
pg_stat_statements (i.e. several queries sent together, eg with psql:
"SELECT 1 \; SELECT 2;").
This bug was found in passing while investigating a strange performance
issue I had with compound statements.
Collect query location information in parser:
* create a ParseNode for statements with location information fields
(qlocation & qlength).
* add these fields to all parsed statements (*Stmt), Query and PlannedStmt.
* statements location is filled in:
- the lexer keep track of the last ';' encountered.
- the information is used by the parser to compute the query length,
which depends on whether the query ended on ';' or on the input end.
- the query location is propagated to Query and PlannedStmt when built.
* the information is used by pg_stat_statement so as to extract the relevant part
of the query string, including some trimming.
* pg_stat_statement validation is greatly extended so as to test options
and exercise various cases, including compound statements.
note 1: two non-statements tags (use for alter table commands) have been
moved so that all statements tags are contiguous and easy to check.
note 2: the impact on the lexer & parser is quite minimal with this
approach, about 30 LOC, most of which in one function. The largest changes
are in the node header to add location fields.
note 3: the query length excludes the final separator, so that
;-terminated and end of input terminated queries show the same.
note 4: the added test suggests that when tracking "all", queries in SQL
user functions are not tracked, this might be a bug.
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