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Fix mat view guide typos #189

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Merged
merged 6 commits into from
May 30, 2025
Merged

Fix mat view guide typos #189

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44e7a60
Fix mat view guide typos
puzpuzpuz May 23, 2025
8a073bf
Remove partitioning from guide example
puzpuzpuz May 23, 2025
f2b41e2
Improve example
puzpuzpuz May 23, 2025
aaeb74a
Remove beta mentioning
puzpuzpuz May 23, 2025
b1d9fa1
Merge branch 'main' into puzpuzpuz_fix_mv_guide_typos
nwoolmer May 30, 2025
a112bd1
Merge branch 'main' into puzpuzpuz_fix_mv_guide_typos
nwoolmer May 30, 2025
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40 changes: 15 additions & 25 deletions documentation/guides/mat-views.md
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Expand Up @@ -106,18 +106,16 @@ If you are unfamiliar with the OHLC concept, please see our

```questdb-sql title="trades_OHLC_15m DDL"
CREATE MATERIALIZED VIEW 'trades_OHLC_15m'
WITH BASE 'trades' REFRESH INCREMENTAL
AS (
SELECT
timestamp, symbol,
first(price) AS open,
max(price) as high,
min(price) as low,
last(price) AS close,
sum(amount) AS volume
FROM trades
SAMPLE BY 15m
) PARTITION BY MONTH;
WITH BASE 'trades' REFRESH INCREMENTAL AS
SELECT
timestamp, symbol,
first(price) AS open,
max(price) as high,
min(price) as low,
last(price) AS close,
sum(amount) AS volume
FROM trades
SAMPLE BY 15m;
```

In this example:
Expand All @@ -132,12 +130,13 @@ In this example:
4. The `SAMPLE BY` query contains two key column (`timestamp`, `symbol`) and
five aggregates (`first`, `max`, `min`, `last`, `price`) calculated in `15m`
time buckets.
5. The view is partitioned by `DAY`.
5. The view is partitioned by `MONTH`. This partitioning is selected
[by default](#default-partitioning) based on the `SAMPLE BY` interval.
6. No TTL is defined
- Therefore, the materialized view will contain a summary of _all_ the base
`trades` table's data.

Many parts of the above DDL statement are optional and can be ommited:
Many parts of the above DDL statement are optional and can be omitted:

```questdb-sql title="trades_OHLC_15m compact DDL"
CREATE MATERIALIZED VIEW 'trades_OHLC_15m' AS
Expand Down Expand Up @@ -357,20 +356,12 @@ useful.

## Limitations

### Beta

- Not all `SAMPLE BY` syntax is supported, for example, `FILL`.
- The `INCREMENTAL` refresh strategy relies on deduplicated inserts (O3 writes)
- We will instead delete a time range and insert the data as an append, which
is **much** faster.
- This also means that currently, deduplication keys must be aligned across
- This means that currently, deduplication keys must be aligned across
the `base` table and the view.

### Post-release

- Only `INCREMENTAL` refresh is supported
- We intend to add alternatives, such as:
- `PERIODIC` (once per partition),
- In next versions, we intend to add alternatives, such as:
- `TIMER` (once per time interval)
- `MANUAL` (only when manually triggered)
- `INCREMENTAL` refresh is only triggered by inserts into the `base` table, not
Expand Down Expand Up @@ -496,7 +487,6 @@ Instead of storing the raw data, we will store one row, per symbol, per side,
per day of data.

```questdb-sql title="down-sampling test query" demo

SELECT timestamp, symbol, side, price, amount, "latest" as timestamp FROM (
SELECT timestamp,
symbol,
Expand Down