Added buckets for queries that take less than minimum histogram time
and one for the ones taking more than the max value specified.
Also, in case the buckets end up overlapping, on server start, an
error will be thrown informing the user of this issue and requesting
a rectification.
Refactored the code to consolidate the calculations in a single
function.
* PG-543: pg_stat_monitor: PostgreSQL's pg_stat_statements compatible view.
The view now carries all the columns as pg_stat_statements. This required fixing
data types of some of the columns, renaming a few, as well inclusion of new
columns to make the view fully compatible with pg_stat_statements.
* PG-543: pg_stat_monitor: PostgreSQL's pg_stat_statements compatible view.
Updating the upgrade sql file from 1.0 to 2.0 version linked with this issue
changes.
* PG-543: pg_stat_monitor: PostgreSQL's pg_stat_statements compatible view.
Updating datum calls to use UInt64 rather than Int64.
* PG-582: blk_read_time and blk_write_time are not being rounded.
Added the round off within the internal function so that values for
blk_read_time, blk_write_time are rounded off to 4 decimal places.
Additionally, added rounding off for the PG15+ columns of
temp_blk_read_time and temp_blk_write_time.
* PG-582: blk_read_time and blk_write_time are not being rounded.
Added rounding off for four JIT related columns introduced for PG15.
The bucket start time reported by pg_stat_monitor does not match the PG time and
timezone. The fix is to use TimestampTz for recording the bucket start time.
pgsm_get_ss() must only be called when pg_stat_monitor.so is loaded.
Fix is to move the pgsm_get_ss() call after checking if the pg_stat_monotor
library is loaded or not.
* PG-488: pg_stat_monitor: Overflow management.
Reimplement the storage mechanism of buckets (for PG-15 onward) and query texts
using Dynamic shared memory. Since the dynamic shared memory can grow into a
swap area, so we get the overflow out of the box.
As PostgreSQL versions prior to V15 does not support sequence scan on dynamic
shared memory hashes, so older versions has to live with the classic shared
memory hash for storing the buckets.
Another noteworthy change with the new design is: it saves the query pointer
inside the bucket, and eventually, the query text gets evicted with the bucket
recycle.
Finally, the dynamic shared memory hash has a built-in locking mechanism, so we
can revisit the whole locking in pg_stat_monitor has the potential for lots of
performance improvements.
* Fixing tap test reported issues and also disabling dynamic hash for all versions
* Updating the expected out file for top_query test case
Co-authored-by: Hamid Akhtar <hamid.akhtar@percona.com>
queryid creation mechanism.
Resolving the crash identified by regression and reported by Naeem.
This fix resolves the issue with incorrect query length in case of
normalized query when the query length exceeds PGSM_QUERY_MAX_LEN.
Resolving the crash identify by regression and reported by Naeem.
Regardless of the database or the user, the same query will yield the
same query ID. As part of this, a new column, 'pgsm_query_id', is added.
* pgsm_query_id:
pgsm_query_id has the same data type of int8 as the queryid column. If
the incoming SQL command includes any constants, it internally normalizes
the query to remove those constant values with placeholders. Otherwise,
it uses the query directly to generate the query hash.
Since we no longer depend on the server's parse tree mechanism, we can
generate the same hash for the same query text for all server versions.
Also, it is important to note that the hash being calculated is a database,
schema and user independent. So same query text in different databases
will generate the same hash.
This column is not part of the key; rather, for observability purposes only.
* Regression
SQL test case pgsm_query_id.sql is added to the SQL regression.
Reimplement the storage mechanism of buckets and query texts
using Dynamic shared memory. Since the dynamic shared memory
can grow into a swap area, so we get the overflow out of the box.
oreover the new design saves the query pointer inside the bucket
and eventually, the query text gets evicted with the bucket recycle.
Finally, the dynamic shared memory hash has a built-in locking
mechanism so we can revisit the whole locking in pg_stat_monitor
has potential for lots of performance improvements
Removing the view for 2.0. Updating the required SQL files to manage
the upgrade. Downgrade from 2.x to 1.x is not supported.
Also part of this fix is the SQL regression. This does not update the
tap test cases.
In line with pg_stat_statments for PG15, This commit adds eight new cumulative
counters for jit operations, making it easier to diagnose how JIT is used in an
installation. And two new columns, temp_blk_read_time, and temp_blk_write_time,
respectively, show the time spent reading and writing temporary file blocks
on disk.
Moreover, The commit also contains a few indentations and API adjustments.
A new column is added to mention that bucket is active or done. there is
some timing based adjustment was required with that too.
Co-authored-by: Hamid Akhtar <hamid.akhtar@percona.com>
Creating the infrastructure that'll allow using newer versions
of the loadable module with old SQL declarations.
Also updating the build version to 2.0.0-dev
There was a typo while checking the PostgreSQL version in the SQL file. This commit
will fix the typo, and only the necessary columns will be visible in the view.
The query status monitoring code was used to track the current query state, for example,
parsing, executing and finishing. After careful review, we have figured out that
it does not make sense while a lot of time same query is running. Therefore it
is also consuming resources. This commit will remove that feature. The upgrade
SQL from 1.0 - 2.0 is also updated.
PG 15 requires additional shared memory and LWLocks requests to be made from the
newly introduced shmem_request_hook and disallows the requests initiated
from outside the hook.
The commit makes moves the additional shared memory and LWLocks requests
from _PG_init to shmem_request_hook for PG15
pg_stat_monitor is a bit longer; therefore, it requires some code cleanup.
Therefore I decided to turn these tasks into multiple commits and PR to avoid
various changes in one PR. This will ease the review and Q/A process.
In this commit, I have done these tasks.
1 - Fixing compilation issue, cause by previous commit, where we removed
the benchmarking code. It was causing problem for PostgreSQL-12.
pg_stat_monitor is a bit longer; therefore, it requires some code cleanup.
Therefore I decided to turn these tasks into multiple commits and PR to avoid
various changes in one PR. This will ease the review and Q/A process.
In this commit, I have done these tasks.
1 - Remove all benchmarking and debugging code.
* PG-475: Inconsistent behaviour of PGSM
Reverting the bucket locking mechanism to previous behavior. This has
a lot of room for improvement that needs to be part of a major refactoring
in the 2.x release.
* PG-481 Release notes 1.1.0 (#294)
modified: RELEASE_NOTES.md
* PG-500: Bump the version of pg_stat_monitor to 1.1.0 (#297)
* PG-501: Missing Buckets and incorrect calls count. (#298)
prev_bucket_sec holds the actual time at which the previous bucket was created
and it is used to compute if the previous bucket time has elapsed and when is
the time to create a new one. But since the bucket start time is rounded down
to logical time window start, that makes the prev_bucket_sec and bucket start
time out of sync with each other, and depending on the query arrival time there
is a high probability that a bucket gets missed especially when the last bucket
was created around the end of the bucket time window.
Solution is to keep the prev_bucket_sec and bucket start time in-sync.
Moreover, we are using the unint64 for storing the prev_bucket_sec which is kind
of an overkill and a simple uint should be good enough for the purpose. But that
change can be taken up as part of the create-bucket function refactoring task.
* PG-501: Missing Buckets and incorrect calls count.
Ensuring the outer bound for the bucket is an exclusive boundary and it
as it belongs to the next bucket. To explain the point further, a set of
five second bucket would be:
Bucket 1: 00:00:00.00 -> 00:00:04.99...
Bucket 2: 00:00:00.05 -> 00:00:09.99...
Bucket 3: 00:00:00.10 -> 00:00:14.99...
...
Co-authored-by: Ibrar Ahmed <ibrar.ahmed@percona.com>
Co-authored-by: Anastasia Alexandrova <anastasia.alexandrova@percona.com>
Co-authored-by: Muhammad Usama <m.usama@gmail.com>
PG-456: Running pgindent to make source indentation/spacing PostgreSQLCompatible.
PostgreSQL uses pgindent from time to time to make source code PostgreSQL
style guide compatible, it is a very long time since we have not done that.
Commit fixes a lot of indentation and spacing issues.
Co-authored-by: Hamid Akhtar <hamid.akhtar@gmail.com>
PG-453: Normalize query does not work with INSERT statements.
The commit fixes the issue similar to pg_stat_statements. Jumble query skips in
case of INSERT statements to avoid the duplicate queryid, but in another
commit we already solved that problem with another way.
The buckets are now created with the start time a modulus of the bucket time size.
So if we have a 10 second bucket, the start times would reflect that:
- Bucket1: 00:00:00
- Bucket2: 00:00:10
- Bucket3: 00:00:20
...
Previously, the start time of the bucket was aligned with the first query that
arrives in that bucket. However, now the behaviour is changed. So, even if the
first query for bucket 2 arrives at 00:00:13, the start time would still be set
to 00:00:10.
This change now makes the bucketing separated out by fixed time windows so that
external applications can easily consume that data and chart it.
Also, as part of this change, locking of pgss is updated now and extended
to last the bucket related changes.
There was no maximum limit set for the number of maximum histograms
bucket, which can lead to a crash in case of higher value.
PG-382: Adjust the maximum value for histogram buckets.
Fix the regression issue for PostgreSQL-12.
PG-382: Adjust the maximum value for histogram buckets.
Fix the TAP test cases.
Similar to pg_stat_statements, pg_stat_monitor tracks wal data metrics
since PostgreSQL 13, the problem was that for PostgreSQL versions 11 and
12 we left the WalUsage variable declared in the stack unitialized,
thus leading to garbage values.
Fixed the problem by ignoring the WalUsage variable value for PG <= 12.
To check if a bucket has expired, a comparison of the time elapsed
since last bucket change was being done in get_next_wbucket() function
using the following line:
while ((current_usec - current_bucket_usec) > (PGSM_BUCKET_TIME
* 1000 * 1000))
The problem is that the expression compares a uint64 (current_usec)
with a int32 (PGSM_BUCKET_TIME), if a given user configures a value for
pgsm_bucket_time GUC (let's call it T) that could overflow int32 range
in the expression T*1000*1000 > 2**31-1, then the result would be a
negative integer cast to (uint64), resulting in a large uint64 value that
would evaluate the expression as false, thus never updating bucket
number.
When querying pg_stat_monitor view, for every entry it's verified if
the entry has not yet expired by calling IsBucketValid(bucket_number).
Using the entry's bucket number the function calculates if the time
since the bucket started, using shared global variable
pgss->bucket_start_time[bucket_id], is still valid.
Since pgss->bucket_start_time is not properly initialized in
get_next_wbucket(), the function IsBucketValid() will always
return false, thus not listing any entries in the view.
There was a missing increment/decrement to exec_nested_level in
pgss_ProcessUtility hook, due to this, some utility statements could
end up being processed more than once, as PostgreSQL may recurse into
this hook for sub-statements or when processing a query string
containing multiple semicolon-separated statements.
If a query exceeds pg_stat_monitor.pgsm_query_max_len, then it's
truncated before we save it into the query buffer (SaveQueryText).
When reading the query back, on pg_stat_monitor_internal, we allocate a
buffer for the query with length = pg_stat_monitor.pgsm_query_max_len,
the problem is that the read_query function adds a '\0' to the end of
the buffer when reading a query, thus if a query has been truncated, for
example, to 1024, when reading it back read_query will store the '\0' at
the position 1025, an out of array bounds position.
Then, when we call pfree to release the buffer, PostgreSQL notices the
buffer overrun and triggers an error assertion, the assertion calls our
error hook which attempts to acquire the shared pgss->lock before
pg_stat_monitor_internal has released it, leading to a deadlock.
To avoid the problem we add 1 more byte to the extra '\0' during palloc
call for query_text and parent_query_text.
Also, we release the lock before calling pfree, just in case PostgreSQL
finds a problem in pfree we won't deadlock again and get the error
reported correctly.
Hamid Akhtar
Muhammad Usama
Ibrar Ahmed
Muhammad Usama
Kai Wagner
Hamid Akhtar
Ibrar Ahmed
Diego Fronza
Ibrar Ahmed