feat: add output_schema method to queries (#2717)

This is a helper utility I need for some of my data loader work. It
makes it easy to see the output schema even when a `select` has been
applied.

docs/src/js/classes/Query.md

@@ -343,6 +343,29 @@ This is useful for pagination.
 
 ***
 
+### outputSchema()
+
+```ts
+outputSchema(): Promise<Schema<any>>
+```
+
+Returns the schema of the output that will be returned by this query.
+
+This can be used to inspect the types and names of the columns that will be
+returned by the query before executing it.
+
+#### Returns
+
+`Promise`&lt;`Schema`&lt;`any`&gt;&gt;
+
+An Arrow Schema describing the output columns.
+
+#### Inherited from
+
+`StandardQueryBase.outputSchema`
+
+***
+
 ### select()
 
 ```ts

docs/src/js/classes/QueryBase.md

@@ -140,6 +140,25 @@ const plan = await table.query().nearestTo([0.5, 0.2]).explainPlan();
 
 ***
 
+### outputSchema()
+
+```ts
+outputSchema(): Promise<Schema<any>>
+```
+
+Returns the schema of the output that will be returned by this query.
+
+This can be used to inspect the types and names of the columns that will be
+returned by the query before executing it.
+
+#### Returns
+
+`Promise`&lt;`Schema`&lt;`any`&gt;&gt;
+
+An Arrow Schema describing the output columns.
+
+***
+
 ### select()
 
 ```ts

docs/src/js/classes/TakeQuery.md

@@ -143,6 +143,29 @@ const plan = await table.query().nearestTo([0.5, 0.2]).explainPlan();
 
 ***
 
+### outputSchema()
+
+```ts
+outputSchema(): Promise<Schema<any>>
+```
+
+Returns the schema of the output that will be returned by this query.
+
+This can be used to inspect the types and names of the columns that will be
+returned by the query before executing it.
+
+#### Returns
+
+`Promise`&lt;`Schema`&lt;`any`&gt;&gt;
+
+An Arrow Schema describing the output columns.
+
+#### Inherited from
+
+[`QueryBase`](QueryBase.md).[`outputSchema`](QueryBase.md#outputschema)
+
+***
+
 ### select()
 
 ```ts

docs/src/js/classes/VectorQuery.md

@@ -498,6 +498,29 @@ This is useful for pagination.
 
 ***
 
+### outputSchema()
+
+```ts
+outputSchema(): Promise<Schema<any>>
+```
+
+Returns the schema of the output that will be returned by this query.
+
+This can be used to inspect the types and names of the columns that will be
+returned by the query before executing it.
+
+#### Returns
+
+`Promise`&lt;`Schema`&lt;`any`&gt;&gt;
+
+An Arrow Schema describing the output columns.
+
+#### Inherited from
+
+`StandardQueryBase.outputSchema`
+
+***
+
 ### postfilter()
 
 ```ts

docs/src/js/interfaces/IvfRqOptions.md

@@ -0,0 +1,101 @@
+[**@lancedb/lancedb**](../README.md) • **Docs**
+
+***
+
+[@lancedb/lancedb](../globals.md) / IvfRqOptions
+
+# Interface: IvfRqOptions
+
+## Properties
+
+### distanceType?
+
+```ts
+optional distanceType: "l2" | "cosine" | "dot";
+```
+
+Distance type to use to build the index.
+
+Default value is "l2".
+
+This is used when training the index to calculate the IVF partitions
+(vectors are grouped in partitions with similar vectors according to this
+distance type) and during quantization.
+
+The distance type used to train an index MUST match the distance type used
+to search the index. Failure to do so will yield inaccurate results.
+
+The following distance types are available:
+
+"l2" - Euclidean distance.
+"cosine" - Cosine distance.
+"dot" - Dot product.
+
+***
+
+### maxIterations?
+
+```ts
+optional maxIterations: number;
+```
+
+Max iterations to train IVF kmeans.
+
+When training an IVF index we use kmeans to calculate the partitions. This parameter
+controls how many iterations of kmeans to run.
+
+The default value is 50.
+
+***
+
+### numBits?
+
+```ts
+optional numBits: number;
+```
+
+Number of bits per dimension for residual quantization.
+
+This value controls how much each residual component is compressed. The more
+bits, the more accurate the index will be but the slower search. Typical values
+are small integers; the default is 1 bit per dimension.
+
+***
+
+### numPartitions?
+
+```ts
+optional numPartitions: number;
+```
+
+The number of IVF partitions to create.
+
+This value should generally scale with the number of rows in the dataset.
+By default the number of partitions is the square root of the number of
+rows.
+
+If this value is too large then the first part of the search (picking the
+right partition) will be slow. If this value is too small then the second
+part of the search (searching within a partition) will be slow.
+
+***
+
+### sampleRate?
+
+```ts
+optional sampleRate: number;
+```
+
+The number of vectors, per partition, to sample when training IVF kmeans.
+
+When an IVF index is trained, we need to calculate partitions. These are groups
+of vectors that are similar to each other. To do this we use an algorithm called kmeans.
+
+Running kmeans on a large dataset can be slow. To speed this up we run kmeans on a
+random sample of the data. This parameter controls the size of the sample. The total
+number of vectors used to train the index is `sample_rate * num_partitions`.
+
+Increasing this value might improve the quality of the index but in most cases the
+default should be sufficient.
+
+The default value is 256.