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PG-254: Add query location to hash table entries.

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Whenever a new query is added to a query buffer, record the position
in which the query was inserted, we can then use this information to
locate the query in a faster way later on when required.

This allowed to simplify the logic in hash_entry_dealloc(), after
creating the list of pending queries, as the list is scanned we can copy
the query from the previous query buffer to the new one by using the
query position (query_pos), this avoids scanning the whole query buffer
when looking up for the queryid.

Also, when moving a query to a new buffer (copy_query), we update
the query_pos for the hash table entry, so it points to the right place
in the new query buffer.

read_query() function was updated to allow query position to be passed
as argument, if pos != 0 use it to locate the query directly, otherwise
fallback to the previous mode of scanning the whole buffer.

SaveQueryText() was updated to pass a reference to the query position as
argument, this value is updated after the function finishes with the
position that the query was stored into the buffer.
This commit is contained in:
Diego Fronza
2021-10-07 10:06:20 -03:00
parent fcb70ffed1
commit 8fdf0946fe
3 changed files with 98 additions and 144 deletions
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10
pg_stat_monitor.h
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@@ -294,6 +294,7 @@ typedef struct pgssEntry
Counters counters; /* the statistics for this query */
int encoding; /* query text encoding */
slock_t mutex; /* protects the counters only */
size_t query_pos; /* query location within query buffer */
} pgssEntry;
/*
@@ -361,7 +362,12 @@ typedef struct JumbleState
/* Links to shared memory state */
bool SaveQueryText(uint64 bucketid, uint64 queryid, unsigned char *buf, const char *query, uint64 query_len);
bool SaveQueryText(uint64 bucketid,
uint64 queryid,
unsigned char *buf,
const char *query,
uint64 query_len,
size_t *query_pos);
/* guc.c */
void init_guc(void);
@@ -385,7 +391,7 @@ pgssEntry* hash_entry_alloc(pgssSharedState *pgss, pgssHashKey *key, int encodin
Size hash_memsize(void);
int read_query_buffer(int bucket_id, uint64 queryid, char *query_txt);
uint64 read_query(unsigned char *buf, uint64 bucketid, uint64 queryid, char * query);
uint64 read_query(unsigned char *buf, uint64 queryid, char * query, size_t pos);
pgssQueryEntry* hash_find_query_entry(uint64 bucket_id, uint64 queryid, uint64 dbid, uint64 userid, uint64 ip, uint64 appid);
pgssQueryEntry* hash_create_query_entry(uint64 bucket_id, uint64 queryid, uint64 dbid, uint64 userid, uint64 ip, uint64 appid);
void pgss_startup(void);