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PG-262: Fix comment extraction on queries. 

The regular expression was updated to properly capture comments in SQL
in the form /* */.

The previous regex was capturing everything from /* until the last */
because regex are greedy, this was presenting problems if a input query
has something like:
SELECT /* comment 1 */ field /* comment 2 */ from FOO;

As such, the previous regex would capture anytying between /* comment 1
and comment 2 */, the result would be:
/* comment 1 field comment 2*/.

Multiline comments are also captured.

Multiple comments in one query are now stored in the pg_stat_monitor
comments field in the form: /* Comment 1 */, ... , /* Comment N */.
pull/123/head
Diego Fronza 2021-10-18 11:41:37 -03:00
parent 350ef723ab
commit a9a36905f2
1 changed files with 30 additions and 5 deletions
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35
pg_stat_monitor.c
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@ -251,7 +251,7 @@ _PG_init(void)
/*
* Compile regular expression for extracting out query comments only once.
*/
rc = regcomp(&preg_query_comments, "/\\*.*\\*/", 0);
rc = regcomp(&preg_query_comments, "/\\*([^*]|[\r\n]|(\\*+([^*/]|[\r\n])))*\\*+/", REG_EXTENDED);
if (rc != 0)
{
elog(ERROR, "pg_stat_monitor: query comments regcomp() failed, return code=(%d)\n", rc);
@ -3461,12 +3461,37 @@ extract_query_comments(const char *query, char *comments, size_t max_len)
int rc;
size_t nmatch = 1;
regmatch_t pmatch;
regoff_t comment_len, total_len = 0;
const char *s = query;
rc = regexec(&preg_query_comments, query, nmatch, &pmatch, 0);
if (rc != 0)
return;
while (total_len < max_len)
{
rc = regexec(&preg_query_comments, s, nmatch, &pmatch, 0);
if (rc != 0)
break;
snprintf(comments, max_len, "%.*s", pmatch.rm_eo - pmatch.rm_so -4, &query[pmatch.rm_so + 2]);
comment_len = pmatch.rm_eo - pmatch.rm_so;
if (total_len + comment_len > max_len)
break; /* TODO: log error in error view, insufficient space for comment. */
total_len += comment_len;
/* Not 1st iteration, append ", " before next comment. */
if (s != query)
{
if (total_len + 2 > max_len)
break; /* TODO: log error in error view, insufficient space for ", " + comment. */
memcpy(comments, ", ", 2);
comments += 2;
total_len += 2;
}
memcpy(comments, s + pmatch.rm_so, comment_len);
comments += comment_len;
s += pmatch.rm_eo;
}
}
#if PG_VERSION_NUM < 140000