@@ -7,22 +7,22 @@ However, in [[Space Lua]] it interpreted as an SQL (and [LINQ](https://learn.mic
General syntax:
query[[
from <var> = <expression>
from <var> in <expression>
where <expression>
order by <expression>
limit <expression>, <expression>
select <expression>
]]
LIQ can operate on any Lua collection.
LIQ operates on any Lua collection.
For instance, to sort a list of numbers in descending order:
${query[[from n = {1, 2, 3} order by n desc]]}
${query[[from n in {1, 2, 3} order by n desc]]}
However, in most cases you’ll use it in conjunction with [[API/index#index.tag(name)]]. Here’s an example querying the 3 pages that were last modified:
${query[[
from p = index.tag "page"
from p in index.tag "page"
order by p.lastModified desc
select p.name
limit 3
@@ -41,50 +41,68 @@ Here are the clauses that are currently supported:
## from <expression>
The `from` clause specifies the source of your data. There are two syntactic variants:
With explicit variable binding:
**Recommended:**With explicit variable binding:
from v in <<expression>>
or
from v = <<expression>>
binding each item to the variable `v`.
And the shorter:
However, there is also the more concise:
from <<expression>>
implicitly binding each item to the variable `_` as well as making all attributes directly available as variables.
implicitly binding each item to the variable `_` as well as making all attributes directly available as variables. The latter, while shorter, is less performant and will block future optimizations, so the variable-binding variant is preferred.
> **warning** Warning
> When you use a `from` clause without explicit variable binding (so without thee `v in` syntax), note that any attribute of the object you’re iterating over will shadow global variables. For instance, if you have an object with a `table` attribute, regular `table` APIs will become inaccessible within the query.
>
> **Recommendation:** Use the explicit variable binding syntax
Example without variable binding:
${query[[from {1, 2, 3} select _]]}
With variable binding:
${query[[from n = {1, 2, 3} select n]]}
${query[[from n in {1, 2, 3} select n]]}
A more realistic example using `index.tag`:
${query[[from index.tag "page" order by lastModified select name limit 3]]}
${query[[from p in index.tag "page" order by p.lastModified select p.name limit 3]]}
## where <expression>
The `where` clause allows you to filter data. When the expression evaluated to a truthy value, the item is included in the result.
Example:
${query[[from {1, 2, 3, 4, 5} where _ > 2]]}
${query[[from n in {1, 2, 3, 4, 5} where n > 2]]}
Or to select all pages tagged with `#meta`:
Or to select 5 pages tagged with `#meta`:
${query[[from index.tag "page" where table.includes(tags, "meta")]]}
${query[[from p in index.tag "page" where table.includes(p.tags, "meta") limit 5]]}
Or select based on name (including folder) and a [[API/string|string function]]
${query[[from index.tag "page" where name:startsWith("Person")]]}
${query[[from p in index.tag "page" where p.name:startsWith("Person")]]}
## order by <expression> [desc]
The `order by` clause allows you to sort data, when `desc` is specified it reverts the sort order.
As an example, the last 3 modified pages:
${query[[
from index.tag "page"
order by lastModified desc
select name
from p in index.tag "page"
order by p.lastModified desc
select p.name
limit 3
]]}
You can order based on multiple expressions by specifying multiple expressions separated by commas:
${query[[
from p in index.tag "page"
order by p.lastModified desc, p.name
select p.name
limit 3
]]}
@@ -107,28 +125,21 @@ The `select` clause allows you to transform each item in the result set. If omit
You can also return tables or other complex values:
It is convenient to combine it with the [[API/table#table.select(table, keys...)]] API:
${query[[
from p = index.tag "page"
select {
name = p.name,
modified = p.lastModified
}
from p in index.tag "page"
select table.select(p, "name", "lastModified")
limit 3
]]}
## Rendering the output
To render the output as a template, you can rely on the fact that queries return Lua tables. For example, to apply a template to render every page as a link:
${template.each(query[[
from index.tag "page"
order by lastModified desc
from p in index.tag "page"
order by p.lastModified desc
limit 3
]], templates.pageItem)}
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