From 290d8a6f5386b7b829da7ba6c1a3636ca2b78122 Mon Sep 17 00:00:00 2001
From: Kannav Sethi <90309433+Kannav02@users.noreply.github.com>
Date: Fri, 11 Oct 2024 11:35:20 -0400
Subject: [PATCH] Issue 798 - Auditing PFMERGE command docs (#975)

---
 docs/src/content/docs/commands/PFMERGE.md | 67 ++++++++++++++---------
 1 file changed, 42 insertions(+), 25 deletions(-)

diff --git a/docs/src/content/docs/commands/PFMERGE.md b/docs/src/content/docs/commands/PFMERGE.md
index a327d3049..9b94e8f68 100644
--- a/docs/src/content/docs/commands/PFMERGE.md
+++ b/docs/src/content/docs/commands/PFMERGE.md
@@ -13,71 +13,88 @@ PFMERGE destkey sourcekey [sourcekey ...]
 
 ## Parameters
 
-- `destkey`: The key where the merged HyperLogLog will be stored. If this key already exists, it will be overwritten.
-- `sourcekey`: One or more keys of the HyperLogLogs that you want to merge. These keys must already exist and contain HyperLogLog data structures.
 
-## Return Value
+| Parameter  | Description                                                                     | Type         | Required |
+|------------|---------------------------------------------------------------------------------|--------------|----------|
+| `destkey`  | The key where the merged HyperLogLog will be stored. If this key already exists, it will be overwritten. | String       | Yes      |
+| `sourcekey`| One or more keys of the HyperLogLogs that you want to merge. These keys must already exist and contain HyperLogLog data. | List[String] | Yes      |
 
-- `Simple String Reply`: Returns `OK` if the merge operation is successful.
+## Return Values
 
-## Behaviour
 
-When the `PFMERGE` command is executed, DiceDB will:
+| Condition                                      | Return Value                                      |
+|------------------------------------------------|---------------------------------------------------|
+| Command is successful                          | `OK`                                              |
+| Syntax or specified constraints are invalid    | `(error)`                                             |
+
 
-1. Retrieve the HyperLogLog data structures from the specified `sourcekey` keys.
-2. Merge these HyperLogLogs into a single HyperLogLog.
-3. Store the resulting HyperLogLog in the `destkey`.
-4. If the `destkey` already exists, its previous value will be overwritten with the new merged HyperLogLog.
+## Behaviour
 
-## Error Handling
+- If the `destkey` already exists, the `PFMERGE` command will overwrite the existing value with the new merged HyperLogLog.
+- The command retrieves the HyperLogLog data structures from the specified `sourcekey` keys.
+- These `sourcekey` keys are merged into a single HyperLogLog and stored in the `destkey`.
+- If the `sourcekey` keys are not valid HyperLogLogs, an error is returned.
+  
+
+## Errors
 
 The `PFMERGE` command can raise errors in the following scenarios:
 
 1. `Wrong Type Error`: If any of the `sourcekey` keys or the `destkey` key contains a value that is not a HyperLogLog, DiceDB will return an error.
 
-   - `Error Message`: `WRONGTYPE Operation against a key holding the wrong kind of value`
+   - `(error)`: `WRONGTYPE Operation against a key holding the wrong kind of value`
 
 2. `Non-Existent Key Error`: If any of the `sourcekey` keys do not exist, DiceDB will treat them as empty HyperLogLogs and proceed with the merge operation without raising an error.
 
 ## Example Usage
 
-### Example 1: Basic Usage
+### Basic Usage
 
 Suppose you have three HyperLogLogs stored at keys `hll1`, `hll2`, and `hll3`, and you want to merge them into a new HyperLogLog stored at key `hll_merged`.
 
 ```sh
-127.0.0.1:6379> PFADD hll1 "a" "b" "c"
+127.0.0.1:7379> PFADD hll1 "a" "b" "c"
 (integer) 1
-127.0.0.1:6379> PFADD hll2 "c" "d" "e"
+127.0.0.1:7379> PFADD hll2 "c" "d" "e"
 (integer) 1
-127.0.0.1:6379> PFADD hll3 "e" "f" "g"
+127.0.0.1:7379> PFADD hll3 "e" "f" "g"
 (integer) 1
-127.0.0.1:6379> PFMERGE hll_merged hll1 hll2 hll3
+127.0.0.1:7379> PFMERGE hll_merged hll1 hll2 hll3
 OK
-127.0.0.1:6379> PFCOUNT hll_merged
+127.0.0.1:7379> PFCOUNT hll_merged
 (integer) 7
 ```
 
-### Example 2: Overwriting Existing Key
+### Overwriting Existing Key
 
 If the `destkey` already exists, it will be overwritten by the merged HyperLogLog.
 
 ```sh
-127.0.0.1:6379> PFADD hll_merged "x" "y" "z"
+127.0.0.1:7379> PFADD hll_merged "x" "y" "z"
 (integer) 1
-127.0.0.1:6379> PFMERGE hll_merged hll1 hll2 hll3
+127.0.0.1:7379> PFMERGE hll_merged hll1 hll2 hll3
 OK
-127.0.0.1:6379> PFCOUNT hll_merged
+127.0.0.1:7379> PFCOUNT hll_merged
 (integer) 7
 ```
 
-### Example 3: Handling Non-Existent Source Keys
+### Handling Non-Existent Source Keys
 
 If a `sourcekey` does not exist, DiceDB will treat it as an empty HyperLogLog.
 
 ```sh
-127.0.0.1:6379> PFMERGE hll_merged hll1 hll2 non_existent_key
+127.0.0.1:7379> PFMERGE hll_merged hll1 hll2 non_existent_key
 OK
-127.0.0.1:6379> PFCOUNT hll_merged
+127.0.0.1:7379> PFCOUNT hll_merged
 (integer) 5
 ```
+
+### Invalid Usage
+
+if a `sourcekey` exists and is not of type HyperLogLog, the command will result in an error
+
+```sh
+127.0.0.1:7379> PFMERGE hll_merged not_hyperLogLog
+(error) WRONGTYPE Key is not a valid HyperLogLog string value.
+
+```
\ No newline at end of file