reverse.rst

reverse

Table of contents

• Description
• Version
• Syntax
• Note
• Example 1: Basic reverse operation
• Example 2: Reverse with sort
• Example 3: Reverse with head
• Example 4: Double reverse
• Example 5: Reverse with complex pipeline

Description

Using reverse command to reverse the display order of search results. The same results are returned, but in reverse order.

Version

3.2.0

Syntax

reverse

• No parameters: The reverse command takes no arguments or options.

Note

The reverse command processes the entire dataset. If applied directly to millions of records, it will consume significant memory resources on the coordinating node. Users should only apply the reverse command to smaller datasets, typically after aggregation operations.

Example 1: Basic reverse operation

The example shows reversing the order of all documents.

PPL query:

os> source=accounts | fields account_number, age | reverse;
fetched rows / total rows = 4/4
+----------------+-----+
| account_number | age |
|----------------+-----|
| 6              | 36  |
| 18             | 33  |
| 1              | 32  |
| 13             | 28  |
+----------------+-----+

Example 2: Reverse with sort

The example shows reversing results after sorting by age in ascending order, effectively giving descending order.

PPL query:

os> source=accounts | sort age | fields account_number, age | reverse;
fetched rows / total rows = 4/4
+----------------+-----+
| account_number | age |
|----------------+-----|
| 6              | 36  |
| 18             | 33  |
| 1              | 32  |
| 13             | 28  |
+----------------+-----+

Example 3: Reverse with head

The example shows using reverse with head to get the last 2 records from the original order.

PPL query:

os> source=accounts | reverse | head 2 | fields account_number, age;
fetched rows / total rows = 2/2
+----------------+-----+
| account_number | age |
|----------------+-----|
| 6              | 36  |
| 18             | 33  |
+----------------+-----+

Example 4: Double reverse

The example shows that applying reverse twice returns to the original order.

PPL query:

os> source=accounts | reverse | reverse | fields account_number, age;
fetched rows / total rows = 4/4
+----------------+-----+
| account_number | age |
|----------------+-----|
| 13             | 28  |
| 1              | 32  |
| 18             | 33  |
| 6              | 36  |
+----------------+-----+

Example 5: Reverse with complex pipeline

The example shows reverse working with filtering and field selection.

PPL query:

os> source=accounts | where age > 30 | fields account_number, age | reverse;
fetched rows / total rows = 3/3
+----------------+-----+
| account_number | age |
|----------------+-----|
| 6              | 36  |
| 18             | 33  |
| 1              | 32  |
+----------------+-----+