wehub-resource-sync
60 lines
1.4 KiB
Markdown
60 lines
1.4 KiB
Markdown
## Index and Limit
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<div class="warning">`limit` cannot be used in conjunction with `index`.</div>
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Initializing a `Table` with an `index` tells Perspective to treat a column as
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the primary key, allowing in-place updates of rows. Only a single column (of any
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type) can be used as an `index`. Indexed `Table` instances allow:
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- In-place _updates_ whenever a new row shares an `index` values with an
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existing row
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- _Partial updates_ when a data batch omits some column.
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- _Removes_ to delete a row by `index`.
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To create an indexed `Table`, provide the `index` property with a string column
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name to be used as an index:
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<div class="javascript">
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JavaScript:
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```javascript
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const indexed_table = await perspective.table(data, { index: "a" });
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```
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</div>
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<div class="python">
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Python
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```python
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indexed_table = perspective.Table(data, index="a");
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```
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</div>
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Initializing a `Table` with a `limit` sets the total number of rows the `Table`
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is allowed to have. When the `Table` is updated, and the resulting size of the
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`Table` would exceed its `limit`, rows that exceed `limit` overwrite the oldest
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rows in the `Table`. To create a `Table` with a `limit`, provide the `limit`
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property with an integer indicating the maximum rows:
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<div class="javascript">
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JavaScript:
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```javascript
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const limit_table = await perspective.table(data, { limit: 1000 });
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```
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</div>
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<div class="python">
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Python:
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```python
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limit_table = perspective.Table(data, limit=1000);
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```
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</div>
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