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pg_ash v1.2

17 Feb 23:27
@NikolayS NikolayS
v1.2
114a34b

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pg_ash 1.2 release notes

51 commits since v1.1. Upgrade from 1.1: \i sql/ash-1.1-to-1.2.sql. Fresh install or upgrade from any version: \i sql/ash-install.sql.

What changed

New: event_queries

event_queries() and event_queries_at() — find which queries are responsible for a specific wait event. Flexible matching: 'Lock:tuple' (exact event), 'IO' (all events of a type), or 'CPU*' (synthetic). Includes bar column.

-- which queries are causing Lock:tuple?
select * from ash.event_queries('Lock:tuple', '1 hour');

-- all IO-related queries in a time window
select * from ash.event_queries_at('IO', '2026-02-17 14:00', '2026-02-17 14:05');

New: session-level color toggle

Enable ANSI colors for the whole session without passing p_color to every call:

set ash.color = on;
select * from ash.top_waits('1 hour');
select * from ash.timeline_chart('1 hour');

Uses a custom GUC — works on any Postgres 9.2+ without postgresql.conf changes. ash.status() now shows the current color state.

New: bar visualization on all wait-showing functions

Every function that shows pct now has a bar column — query_waits, top_by_type, event_queries (plus all _at variants). Bar width controlled by p_width (default 20), colors by p_color or set ash.color = on.

Changed: waits_by_type renamed to top_by_type

Consistent naming with top_waits, top_queries. The old name is dropped on install/upgrade.

Changed: top_queries_with_text columns

mean_time_ms renamed to mean_exec_time_ms. New column total_exec_time_ms added.

Improved: pspg-compatible bar alignment

ANSI color escapes are zero-padded to uniform 19-byte length (\033[38;2;080;250;123m not \033[38;2;80;250;123m). The _bar() helper pads the full bar string to a fixed raw byte length, preventing right-border misalignment in pspg and similar tools.

Improved: timeline_chart shows empty buckets

Quiet periods now show rows with active = 0 instead of being omitted, so you can see the full time range.

Improved: observer-effect protection

The sampler pg_cron command now includes SET statement_timeout = '500ms' to prevent take_sample() from becoming a problem on overloaded servers. The 500ms cap gives 10× headroom over normal ~50ms execution. Existing cron jobs are updated automatically on upgrade.

Improved: version tracking

ash.config now has a version column. ash.status() shows it as the first metric. The install and migration files set it automatically.

Improved: dynamic overload cleanup

ash-install.sql discovers and drops all stale function overloads by name, making it safe to run on any prior version without "function is not unique" errors.

Fixed: event_queries crash without pg_stat_statements

Both event_queries() and event_queries_at() would crash on Postgres instances without pg_stat_statements loaded — the table reference was validated at plan time even in the false branch. Split into two RETURN QUERY branches.

Fixed: IdleTx color in top_by_type

top_by_type() passed 'IdleTx:*' to _wait_color() which used exact match. Changed to LIKE 'IdleTx%'.

Fixed: upgrade path completeness

start() and status() are now re-created in the 1.1→1.2 migration, ensuring upgraded installs get the statement_timeout protection and color/version metrics.

Security: admin functions restricted

start(), stop(), uninstall(), rotate(), and take_sample() are now REVOKEd from PUBLIC and GRANTed only to the schema owner. Reader functions remain PUBLIC.

Security: uninstall confirmation guard

ash.uninstall() now requires a confirmation parameter: ash.uninstall('yes'). Calling without the argument raises an error with usage instructions.

Fixed: status() missing SET jit = off

status() was the only reader function without JIT protection. Fixed.

Functions (37 total)

Function Description
event_queries(event, interval, limit, width, color) New — top queries for a wait event
event_queries_at(event, start, end, limit, width, color) New — absolute-time variant
_bar(event, pct, max_pct, width, color) New — shared bar rendering helper
_color_on(color) New — resolve effective color state (param or session GUC)
top_by_type(interval, width, color) Renamed from waits_by_type — now with bar
top_by_type_at(start, end, width, color) Renamed from waits_by_type_at — now with bar
query_waits(query_id, interval, width, color) Enhanced — added bar column
query_waits_at(query_id, start, end, width, color) Enhanced — added bar column
top_queries_with_text(interval, limit) Enhanced — renamed/added columns
start(interval) Enhanced — statement_timeout in cron command
status() Enhanced — shows version, color state

All other functions unchanged from 1.1. See README for the full reference.

pg_ash 1.1 release notes

Upgrade from 1.0: \i sql/ash-1.1.sql — safe to run on top of a running 1.0 installation.

What changed

New: timeline chart

timeline_chart() and timeline_chart_at() — stacked bar chart of wait events over time, showing average active sessions per bucket. Each rank gets a distinct character — █ (rank 1), ▓ (rank 2), ░ (rank 3), ▒ (rank 4+), · (Other) — so the breakdown is visible without color. ANSI colors are available as an experimental feature via p_color => true — green = CPU*, blue = IO, red = Lock, pink = LWLock, cyan = IPC, yellow = Client, orange = Timeout, teal = BufferPin, purple = Activity, light purple = Extension, light yellow = IdleTx. Colors are aligned with PostgresAI monitoring. Note: psql's table formatter escapes ANSI codes; colors work in pgcli, DataGrip, unaligned mode, or piped output.

select * from ash.timeline_chart('1 hour', '5 minutes');
select * from ash.timeline_chart_at('2026-02-14 19:50', '2026-02-14 20:10', '1 minute', 5, 50);

Output: 4 columns — bucket_start | active | detail | chart. First row is a legend. p_top controls how many events get individual bars (the rest roll into "Other"). Default p_top = 3.

Changed: histogram folded into top_waits

histogram() and histogram_at() removed. The bar column is now part of top_waits() and top_waits_at(), controlled by the p_width parameter (default 40). Same visualization, fewer functions.

Changed: ANSI colors (experimental, off by default)

Color scheme aligned with PostgresAI monitoring: green = CPU*, blue = IO, red = Lock, pink = LWLock, cyan = IPC, yellow = Client, orange = Timeout, teal = BufferPin, purple = Activity, light purple = Extension, light yellow = IdleTx. All colors use 24-bit RGB escape codes for consistent rendering across terminal themes.

Fixed: pg_cron version comparison

Version check now uses string_to_array()::int[] comparison instead of lexicographic string comparison. The old code would incorrectly reject pg_cron 1.10+.

Fixed: check constraint tightened

Minimum valid encoded array is 3 elements ([-wid, count, qid]), not 2. The CHECK constraint and sampler guard now enforce array_length >= 3.

Improved: 100% test coverage

CI expanded from 16 assertions to 151. All 32 functions are directly tested across Postgres 14–18.

Functions (32 total)

Function Description
timeline_chart(interval, bucket, top, width, color) New — stacked bar chart (ANSI colors opt-in)
timeline_chart_at(start, end, bucket, top, width) New — absolute-time variant
_wait_color(event, color) New — ANSI color mapper (experimental)
top_waits(interval, limit, width) Top wait events with bar chart (was without width in 1.0)
top_waits_at(start, end, limit, width) Absolute-time variant with bar chart

All other functions unchanged from 1.0. See README for the full reference.

pg_ash 1.0 release notes

The first release of pg_ash — active session history for Postgres.

What it does

pg_ash samples pg_stat_activity every second via pg_cron and stores wait events, query IDs, and session state in a compact encoded format. The data is queryable with plain SQL through 17 built-in reader functions covering daily review, incident investigation, and trend analysis.

Design philosophy

The anti-extension. pg_ash is pure SQL + PL/pgSQL — no C code, no shared_preload_libraries, no restart required. Install with \i sql/ash-1.0.sql on any Postgres 14+ instance with pg_cron 1.5+, including managed providers: RDS, Cloud SQL, AlloyDB, Supabase, Neon.

Key design decisions:

  • Skytools PGQ-style 3-partition ring buffer — TRUNCATE-based rotation, zero bloat, zero vacuum overhead on sample data
  • Partitioned query_map — three per-partition dictionary tables that TRUNCATE in lockstep with sample partitions, eliminating all GC logic
  • Encoded integer arrays — wait events and query IDs packed into integer[] columns (~106 bytes per row for 6 active backends), with TOAST LZ4 compression
  • Inline SQL decode — reader functions use generate_subscripts and array subscript access instead of plpgsql loops, achieving ~30 ms response times on 1-hour windows
  • Per-function set jit = off — prevents 10x overhead from JIT compilation on OLTP servers without affecting other workloads

Reader functions

17 functions organized into relative-time (interval) and absolute-time (timestamptz range) variants:

Function Description
top_waits(interval, limit) Top wait events with "Other" rollup row
top_queries(interval, limit) Top queries by wait sample count
top_queries_with_text(interval, limit) Same, with query text from pg_stat_statements
query_waits(query_id, interval) Wait event profile for a specific query
waits_by_type(interval) Wait event type distribution
`wait_timeline...
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pg_ash 1.1

16 Feb 21:51
@NikolayS NikolayS
v1.1
536e26f

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pg_ash 1.1

pg_ash 1.1 release notes

Upgrade from 1.0: \i sql/ash--1.1.sql — safe to run on top of a running 1.0 installation.

What changed

New: timeline chart

timeline_chart() and timeline_chart_at() — stacked bar chart of wait events over time, showing average active sessions per bucket. Each rank gets a distinct character — █ (rank 1), ▓ (rank 2), ░ (rank 3), ▒ (rank 4+), · (Other) — so the breakdown is visible even without color. In psql, bars are also ANSI color-coded by wait type: bright green = CPU*, red = Lock, blue = IO, yellow = IdleTx, bright yellow = LWLock, magenta = Client/Extension, cyan = Other.

select * from ash.timeline_chart('1 hour', '5 minutes');
select * from ash.timeline_chart_at('2026-02-14 19:50', '2026-02-14 20:10', '1 minute', 5, 50);

Output: 4 columns — bucket_start | active | detail | chart. First row is a color legend. p_top controls how many events get individual bars (the rest roll into "Other"). Default p_top = 3.

Changed: histogram folded into top_waits

histogram() and histogram_at() removed. The bar column is now part of top_waits() and top_waits_at(), controlled by the p_width parameter (default 40). Same visualization, fewer functions.

Changed: IdleTx gets its own color

IdleTx (idle-in-transaction) now renders as yellow (\033[33m) in timeline charts, distinguishable from CPU* (bright green, \033[92m).

Fixed: pg_cron version comparison

Version check now uses string_to_array()::int[] comparison instead of lexicographic string comparison. The old code would incorrectly reject pg_cron 1.10+.

Fixed: check constraint tightened

Minimum valid encoded array is 3 elements ([-wid, count, qid]), not 2. The CHECK constraint and sampler guard now enforce array_length >= 3.

Improved: 100% test coverage

CI expanded from 16 assertions to 151. All 32 functions are directly tested across Postgres 14–18.

Functions (32 total)

Function Description
timeline_chart(interval, bucket, top, width) New — stacked bar chart with ANSI colors
timeline_chart_at(start, end, bucket, top, width) New — absolute-time variant
_wait_color(event) New — ANSI color mapper for wait event types
top_waits(interval, limit, width) Top wait events with bar chart (was without width in 1.0)
top_waits_at(start, end, limit, width) Absolute-time variant with bar chart

All other functions unchanged from 1.0. See README for the full reference.

pg_ash 1.0 release notes

The first release of pg_ash — active session history for Postgres.

What it does

pg_ash samples pg_stat_activity every second via pg_cron and stores wait events, query IDs, and session state in a compact encoded format. The data is queryable with plain SQL through 17 built-in reader functions covering daily review, incident investigation, and trend analysis.

Design philosophy

The anti-extension. pg_ash is pure SQL + PL/pgSQL — no C code, no shared_preload_libraries, no restart required. Install with \i sql/ash--1.0.sql on any Postgres 14+ instance with pg_cron 1.5+, including managed providers: RDS, Cloud SQL, AlloyDB, Supabase, Neon.

Key design decisions:

  • Skytools PGQ-style 3-partition ring buffer — TRUNCATE-based rotation, zero bloat, zero vacuum overhead on sample data
  • Partitioned query_map — three per-partition dictionary tables that TRUNCATE in lockstep with sample partitions, eliminating all GC logic
  • Encoded integer arrays — wait events and query IDs packed into integer[] columns (~106 bytes per row for 6 active backends), with TOAST LZ4 compression
  • Inline SQL decode — reader functions use generate_subscripts and array subscript access instead of plpgsql loops, achieving ~30 ms response times on 1-hour windows
  • Per-function set jit = off — prevents 10x overhead from JIT compilation on OLTP servers without affecting other workloads

Reader functions

17 functions organized into relative-time (interval) and absolute-time (timestamptz range) variants:

Function Description
top_waits(interval, limit) Top wait events with "Other" rollup row
top_queries(interval, limit) Top queries by wait sample count
top_queries_with_text(interval, limit) Same, with query text from pg_stat_statements
query_waits(query_id, interval) Wait event profile for a specific query
waits_by_type(interval) Wait event type distribution
wait_timeline(interval, bucket) Time-bucketed wait event breakdown
samples_by_database(interval) Per-database sample counts
activity_summary(interval) One-call overview — peak backends, top waits, top queries
histogram(interval, limit, width) Visual bar chart of wait event distribution
samples(interval, limit) Fully decoded raw sample browser

Absolute-time variants (_at suffix): top_waits_at, top_queries_at, query_waits_at, waits_by_type_at, wait_timeline_at, histogram_at, samples_at.

Examples

-- what happened overnight?
select * from ash.activity_summary('8 hours');
        metric        |            value
----------------------+------------------------------
 time_range           | 08:00:00
 total_samples        | 28800
 avg_active_backends  | 16.4
 peak_active_backends | 25
 peak_time            | 2026-02-14 03:17:42+00
 databases_active     | 3
 top_wait_1           | CPU* (35.00%)
 top_wait_2           | Lock:tuple (20.00%)
 top_wait_3           | LWLock:WALWrite (13.00%)
 top_query_1          | 1234567890 (36.00%)
 top_query_2          | 9876543210 (22.00%)
 top_query_3          | 5555555555 (19.00%)

-- visual wait event distribution
select * from ash.top_waits('1 hour');
     wait_event       | samples |  pct  |                    bar
----------------------+---------+-------+-------------------------------------------
 CPU*                 |   18900 | 35.00 | █████████████████████████████████████ 35.00%
 Lock:tuple           |   10800 | 20.00 | █████████████████████ 20.00%
 LWLock:WALWrite      |    7020 | 13.00 | ██████████████ 13.00%
 IO:DataFileWrite     |    5940 | 11.00 | ████████████ 11.00%
 IO:DataFileRead      |    4590 |  8.50 | █████████ 8.50%
 Client:ClientRead    |    2700 |  5.00 | █████ 5.00%
 Timeout:PgSleep      |    1890 |  3.50 | ████ 3.50%
 LWLock:BufferIO      |    1080 |  2.00 | ██ 2.00%
 Lock:transactionid   |     648 |  1.20 | █ 1.20%
 Other                |     432 |  0.80 | █ 0.80%

-- decoded raw samples with query text
select * from ash.samples('10 minutes', 20);
       sample_time        | database_name | active_backends |   wait_event    |  query_id  |                query_text
--------------------------+---------------+-----------------+-----------------+------------+------------------------------------------
 2026-02-14 20:40:10+00   | mydb          |              12 | CPU*            | 1234567890 | select * from orders where created_at > ...
 2026-02-14 20:40:10+00   | mydb          |              12 | IO:DataFileRead | 9876543210 | update inventory set quantity = quantit...
 2026-02-14 20:40:10+00   | mydb          |              12 | Lock:tuple      | 5555555555 | insert into events (type, payload) valu...

Lifecycle functions

Function Description
start(interval) Start sampling — creates pg_cron jobs
stop() Stop sampling — removes pg_cron jobs
status() Show configuration, slot state, and storage metrics
uninstall() Stop sampling and drop the ash schema

Storage characteristics

Measured with representative workloads (see benchmarks):

  • Row size: ~106 bytes for 6 active backends (measured with pg_column_size)
  • Daily storage: ~30 MiB for typical workloads at 1-second sampling
  • Production max: ~60 MiB active (2 partitions x 30 MiB/day for 50 backends)
  • WAL: ~29 KiB per sample steady state (~2.4 GiB/day), dominated by full-page writes

Encoding format

Each sample row contains an integer[] column with the format:

[-wait_id, count, qid, qid, ..., -next_wait_id, count, qid, ...]

Negative values are wait event dictionary IDs (markers), followed by a backend count, then query_map IDs for each backend in that wait state. The encoding version is tracked in ash.config.encoding_version.

Synthetic wait types

  • CPU* — active backend with no wait event reported. The asterisk signals ambiguity: either genuine CPU work or an uninstrumented code path. See gaps.wait.events for details.
  • IdleTx — idle-in-transaction backend with no wait event. These hold locks and block vacuum — always sampled.

Requirements

  • Postgres 14+ (requires query_id in pg_stat_activity)
  • pg_cron 1.5+ for sub-minute scheduling (most managed providers ship this)
  • Optional: pg_stat_statements for top_queries_with_text()
  • compute_query_id = on (default since Postgres 14)

Schema

All objects live in the ash schema:

  • ash.config — singleton configuration table
  • ash.wait_event_map — wait event dictionary (~600 entries max)
  • ash.query_map_0, query_map_1, query_map_2 — per-partition query ID dictionaries
  • ash.query_map_all — unified view (planner eliminates non-matching partitions)
  • ash.sample — partitioned sample table (3 partitions, ring buffer)
  • Indexes on sample_ts per partition for time-range queries

Design documents

Detailed design blueprints are in the blueprints/ directory:

  • SPEC.md — full specification: goals, problem statement, design decisions, encoding format, sampling strategy
  • STORAGE_BRAINSTORM.md — storage format benchmarks comparing 8 approaches (flat rows, JSONB, hstore, smallint[], integer[], and more) with measured bytes/ro...
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pg_ash 1.0 — Active Session History for Postgres

15 Feb 02:54
@NikolayS NikolayS
v1.0
ad34b5f

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pg_ash 1.0 — Active Session History for Postgres

pg_ash 1.0 release notes

The first release of pg_ash — active session history for Postgres.

What it does

pg_ash samples pg_stat_activity every second via pg_cron and stores wait events, query IDs, and session state in a compact encoded format. The data is queryable with plain SQL through 17 built-in reader functions covering daily review, incident investigation, and trend analysis.

Design philosophy

The anti-extension. pg_ash is pure SQL + PL/pgSQL — no C code, no shared_preload_libraries, no restart required. Install with \i ash--1.0.sql on any Postgres 14+ instance with pg_cron 1.5+, including managed providers: RDS, Cloud SQL, AlloyDB, Supabase, Neon.

Key design decisions:

  • Skytools PGQ-style 3-partition ring buffer — TRUNCATE-based rotation, zero bloat, zero vacuum overhead on sample data
  • Partitioned query_map — three per-partition dictionary tables that TRUNCATE in lockstep with sample partitions, eliminating all GC logic
  • Encoded integer arrays — wait events and query IDs packed into integer[] columns (~106 bytes per row for 6 active backends), with TOAST LZ4 compression
  • Inline SQL decode — reader functions use generate_subscripts and array subscript access instead of plpgsql loops, achieving ~30 ms response times on 1-hour windows
  • Per-function set jit = off — prevents 10x overhead from JIT compilation on OLTP servers without affecting other workloads

Reader functions

17 functions organized into relative-time (interval) and absolute-time (timestamptz range) variants:

Function Description
top_waits(interval, limit) Top wait events with "Other" rollup row
top_queries(interval, limit) Top queries by wait sample count
top_queries_with_text(interval, limit) Same, with query text from pg_stat_statements
query_waits(query_id, interval) Wait event profile for a specific query
waits_by_type(interval) Wait event type distribution
wait_timeline(interval, bucket) Time-bucketed wait event breakdown
samples_by_database(interval) Per-database sample counts
activity_summary(interval) One-call overview — peak backends, top waits, top queries
histogram(interval, buckets, width) Visual bar chart using Unicode blocks
samples(interval, limit) Fully decoded raw sample browser

Absolute-time variants (_at suffix): top_waits_at, top_queries_at, query_waits_at, waits_by_type_at, wait_timeline_at, histogram_at, samples_at.

Examples

-- what happened overnight?
select * from ash.activity_summary('8 hours');
        metric        |            value
----------------------+------------------------------
 time_range           | 08:00:00
 total_samples        | 28800
 avg_active_backends  | 16.4
 peak_active_backends | 25
 peak_time            | 2026-02-14 03:17:42+00
 databases_active     | 3
 top_wait_1           | CPU* (35.00%)
 top_wait_2           | Lock:tuple (20.00%)
 top_wait_3           | LWLock:WALWrite (13.00%)
 top_query_1          | 1234567890 (36.00%)
 top_query_2          | 9876543210 (22.00%)
 top_query_3          | 5555555555 (19.00%)

-- visual wait event distribution
select * from ash.histogram('1 hour');
     wait_event       | samples |  pct  |                    bar
----------------------+---------+-------+-------------------------------------------
 CPU*                 |   18900 | 35.00 | █████████████████████████████████████ 35.00%
 Lock:tuple           |   10800 | 20.00 | █████████████████████ 20.00%
 LWLock:WALWrite      |    7020 | 13.00 | ██████████████ 13.00%
 IO:DataFileWrite     |    5940 | 11.00 | ████████████ 11.00%
 IO:DataFileRead      |    4590 |  8.50 | █████████ 8.50%
 Client:ClientRead    |    2700 |  5.00 | █████ 5.00%
 Timeout:PgSleep      |    1890 |  3.50 | ████ 3.50%
 LWLock:BufferIO      |    1080 |  2.00 | ██ 2.00%
 Lock:transactionid   |     648 |  1.20 | █ 1.20%
 Other                |     432 |  0.80 | █ 0.80%

-- decoded raw samples with query text
select * from ash.samples('10 minutes', 20);
       sample_time        | database_name | active_backends |   wait_event    |  query_id  |                query_text
--------------------------+---------------+-----------------+-----------------+------------+------------------------------------------
 2026-02-14 20:40:10+00   | mydb          |              12 | CPU*            | 1234567890 | select * from orders where created_at > ...
 2026-02-14 20:40:10+00   | mydb          |              12 | IO:DataFileRead | 9876543210 | update inventory set quantity = quantit...
 2026-02-14 20:40:10+00   | mydb          |              12 | Lock:tuple      | 5555555555 | insert into events (type, payload) valu...

Lifecycle functions

Function Description
start(interval) Start sampling — creates pg_cron jobs
stop() Stop sampling — removes pg_cron jobs
status() Show configuration, slot state, and storage metrics
uninstall() Stop sampling and drop the ash schema

Storage characteristics

Measured with representative workloads (see benchmarks):

  • Row size: ~106 bytes for 6 active backends (measured with pg_column_size)
  • Daily storage: ~30 MiB for typical workloads at 1-second sampling
  • Production max: ~60 MiB active (2 partitions x 30 MiB/day for 50 backends)
  • WAL: ~29 KiB per sample steady state (~2.4 GiB/day), dominated by full-page writes

Encoding format

Each sample row contains an integer[] column with the format:

[-wait_id, count, qid, qid, ..., -next_wait_id, count, qid, ...]

Negative values are wait event dictionary IDs (markers), followed by a backend count, then query_map IDs for each backend in that wait state. The encoding version is tracked in ash.config.encoding_version.

Synthetic wait types

  • CPU* — active backend with no wait event reported. The asterisk signals ambiguity: either genuine CPU work or an uninstrumented code path. See gaps.wait.events for details.
  • IdleTx — idle-in-transaction backend with no wait event. These hold locks and block vacuum — always sampled.

Requirements

  • Postgres 14+ (requires query_id in pg_stat_activity)
  • pg_cron 1.5+ for sub-minute scheduling (most managed providers ship this)
  • Optional: pg_stat_statements for top_queries_with_text()
  • compute_query_id = on (default since Postgres 14)

Schema

All objects live in the ash schema:

  • ash.config — singleton configuration table
  • ash.wait_event_map — wait event dictionary (~600 entries max)
  • ash.query_map_0, query_map_1, query_map_2 — per-partition query ID dictionaries
  • ash.query_map_all — unified view (planner eliminates non-matching partitions)
  • ash.sample — partitioned sample table (3 partitions, ring buffer)
  • Indexes on sample_ts per partition for time-range queries

Design documents

Detailed design blueprints are in the blueprints/ directory:

  • SPEC.md — full specification: goals, problem statement, design decisions, encoding format, sampling strategy
  • STORAGE_BRAINSTORM.md — storage format benchmarks comparing 8 approaches (flat rows, JSONB, hstore, smallint[], integer[], and more) with measured bytes/row on Postgres 17
  • PARTITIONED_QUERYMAP_DESIGN.md — per-partition query_map design: why single-table GC was replaced with lockstep TRUNCATE, edge cases, trade-offs
  • ROLLUP_DESIGN.md — two-level aggregation design (per-minute 30-day, per-hour 5-year) for long-term trend analysis — planned for v1.1

Benchmark results are published in issue #1.

What is not in 1.0

  • Rollup tables — per-minute and per-hour aggregation for long-term trends (designed in blueprints/ROLLUP_DESIGN.md, implementation planned for 1.1)
  • Cross-database query text — sampling covers all databases (via pg_stat_activity.datid), but top_queries_with_text() can only resolve query text from pg_stat_statements in the database where pg_ash is installed
  • Parallel query attribution — parallel workers are sampled but not linked to their leader
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