Merge pull request #64911 from Blargian/document_lowCardinalityXYZ

[Docs] add `lowCardinalityKeys`, `lowCardinalityIndices` to docs

docs/en/sql-reference/functions/other-functions.md

@@ -212,7 +212,7 @@ toTypeName(x)
 
 ## blockSize {#blockSize}
 
-In ClickHouse, queries are processed in blocks (chunks).
+In ClickHouse, queries are processed in [blocks](../../development/architecture.md/#block-block) (chunks).
 This function returns the size (row count) of the block the function is called on.
 
 **Syntax**
@@ -221,6 +221,33 @@ This function returns the size (row count) of the block the function is called o
 blockSize()
 ```
 
+**Example**
+
+Query:
+
+```sql
+DROP TABLE IF EXISTS test;
+CREATE TABLE test (n UInt8) ENGINE = Memory;
+
+INSERT INTO test
+SELECT * FROM system.numbers LIMIT 5;
+
+SELECT blockSize()
+FROM test;
+```
+
+Result:
+
+```response
+   ┌─blockSize()─┐
+1. │           5 │
+2. │           5 │
+3. │           5 │
+4. │           5 │
+5. │           5 │
+   └─────────────┘ 
+```
+
 ## byteSize
 
 Returns an estimation of uncompressed byte size of its arguments in memory.
@@ -3688,3 +3715,108 @@ Result:
 ```response
 {'version':'1','serial_number':'2D9071D64530052D48308473922C7ADAFA85D6C5','signature_algo':'sha256WithRSAEncryption','issuer':'/CN=marsnet.local CA','not_before':'May  7 17:01:21 2024 GMT','not_after':'May  7 17:01:21 2025 GMT','subject':'/CN=chnode1','pkey_algo':'rsaEncryption'}
 ```
+
+## lowCardinalityIndices
+
+Returns the position of a value in the dictionary of a [LowCardinality](../data-types/lowcardinality.md) column. Positions start at 1. Since LowCardinality have per-part dictionaries, this function may return different positions for the same value in different parts.
+
+**Syntax**
+
+```sql
+lowCardinalityIndices(col)
+```
+
+**Arguments**
+
+- `col` — a low cardinality column. [LowCardinality](../data-types/lowcardinality.md).
+
+**Returned value**
+
+- The position of the value in the dictionary of the current part. [UInt64](../data-types/int-uint.md).
+
+**Example**
+
+Query:
+
+```sql
+DROP TABLE IF EXISTS test;
+CREATE TABLE test (s LowCardinality(String)) ENGINE = Memory;
+
+-- create two parts:
+
+INSERT INTO test VALUES ('ab'), ('cd'), ('ab'), ('ab'), ('df');
+INSERT INTO test VALUES ('ef'), ('cd'), ('ab'), ('cd'), ('ef');
+
+SELECT s, lowCardinalityIndices(s) FROM test;
+```
+
+Result:
+
+```response
+   ┌─s──┬─lowCardinalityIndices(s)─┐
+1. │ ab │                        1 │
+2. │ cd │                        2 │
+3. │ ab │                        1 │
+4. │ ab │                        1 │
+5. │ df │                        3 │
+   └────┴──────────────────────────┘
+    ┌─s──┬─lowCardinalityIndices(s)─┐
+ 6. │ ef │                        1 │
+ 7. │ cd │                        2 │
+ 8. │ ab │                        3 │
+ 9. │ cd │                        2 │
+10. │ ef │                        1 │
+    └────┴──────────────────────────┘
+```
+## lowCardinalityKeys
+
+Returns the dictionary values of a [LowCardinality](../data-types/lowcardinality.md) column. If the block is smaller or larger than the dictionary size, the result will be truncated or extended with default values. Since LowCardinality have per-part dictionaries, this function may return different dictionary values in different parts.
+
+**Syntax**
+
+```sql
+lowCardinalityIndices(col)
+```
+
+**Arguments**
+
+- `col` — a low cardinality column. [LowCardinality](../data-types/lowcardinality.md).
+
+**Returned value**
+
+- The dictionary keys. [UInt64](../data-types/int-uint.md).
+
+**Example**
+
+Query:
+
+```sql
+DROP TABLE IF EXISTS test;
+CREATE TABLE test (s LowCardinality(String)) ENGINE = Memory;
+
+-- create two parts:
+
+INSERT INTO test VALUES ('ab'), ('cd'), ('ab'), ('ab'), ('df');
+INSERT INTO test VALUES ('ef'), ('cd'), ('ab'), ('cd'), ('ef');
+
+SELECT s, lowCardinalityKeys(s) FROM test;
+```
+
+Result:
+
+```response
+   ┌─s──┬─lowCardinalityKeys(s)─┐
+1. │ ef │                       │
+2. │ cd │ ef                    │
+3. │ ab │ cd                    │
+4. │ cd │ ab                    │
+5. │ ef │                       │
+   └────┴───────────────────────┘
+    ┌─s──┬─lowCardinalityKeys(s)─┐
+ 6. │ ab │                       │
+ 7. │ cd │ ab                    │
+ 8. │ ab │ cd                    │
+ 9. │ ab │ df                    │
+10. │ df │                       │
+    └────┴───────────────────────┘
+```

utils/check-style/aspell-ignore/en/aspell-dict.txt

@@ -1935,6 +1935,8 @@ london
 lookups
 loongarch
 lowcardinality
+lowCardinalityIndices
+lowCardinalityKeys
 lowerUTF
 lowercased
 lttb