Source: https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/executions/limits/
Documentation version: v5.3.2

# Configure limits on resource usage

Add a `SET_VAR` hint at the start of a GQL query to set options such as its memory limit and execution parallelism. The hint uses `/*+ ... */` syntax and applies only to the current query. Subsequent queries continue to use the session configuration.

Common options include:

 | Configuration option | Purpose
 | `memory_limit_bytes` | Memory limit for query execution, in bytes.
 | `query_concurrency` | Maximum number of execution threads for a single query.
 | `procedure_minloglevel` | Minimum log level for GQL procedures in the current query.

The 1 GB data-size limit in NebulaGraph Database Developer Edition restricts how much data an instance can store. `memory_limit_bytes` limits memory used during query execution. Changing it does not change the data-size limit. See [Capabilities and limits](https://dev-docs.nebula-graph.io/v5.3.2/intro/limitations/) for product limits.

## Examples

The memory and parallelism examples below use the `movie` graph from the [movie example dataset](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/overview/example-dataset/). If you have not loaded the data, follow [Load the sample data](https://dev-docs.nebula-graph.io/v5.3.2/get-started/first-query/#load) first.

Run the statements one at a time in CONSOLE in NebulaGraph Studio. In `ngql`, place each `'''` delimiter on its own line around a multiline statement. See [Multiline input](https://dev-docs.nebula-graph.io/v5.3.2/get-started/first-query/#ngql).

The values `query_concurrency=2` and `memory_limit_bytes=134217728` illustrate how to set these options. They are not recommended configuration values. Start with the defaults and adjust them for the query and available CPU and memory.

### Configure memory limit

Set the memory limit for the current query to 128 MiB, or `134217728` bytes (128 × 1024 × 1024 bytes):

````
/*+ SET_VAR(memory_limit_bytes=134217728) */
USE movie
MATCH (person:Person)
RETURN person
LIMIT 100

````

If the query exceeds the memory limit, it fails with a memory-limit error. `LIMIT 100` limits the number of rows returned; it does not determine the memory limit the query needs.

### Configure query parallelism

Set the maximum number of execution threads for the current query to `2`:

````
/*+ SET_VAR(query_concurrency=2) */
USE movie
MATCH (person:Person)
RETURN person
LIMIT 100

````

The actual number of threads depends on the execution plan and available CPU resources. Without this hint, the query uses the session configuration. The system default for this option is `1`.

### Configure multiple limits

Set both the maximum number of execution threads to `2` and the memory limit to 128 MiB for the current query:

````
/*+ SET_VAR(query_concurrency=2) SET_VAR(memory_limit_bytes=134217728) */
USE movie
MATCH (person:Person)
RETURN person
LIMIT 100

````

### Configure the minimum log level

This example uses temporary graph `#movie_temporary_graph`. Create it first as described in [CREATE TEMPORARY GRAPH](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/ddl/graph-projection/create/).

````
/*+ SET_VAR(procedure_minloglevel="DEBUG") */ USE #movie_temporary_graph {
  LOG_DEBUG("This is a debug log")
  LOG_INFO("This is an info log")
  LOG_WARN("This is a warning log")
  LOG_ERROR("This is an error log")
}

````

The hint sets the minimum procedure log level to `DEBUG` for the current query, allowing logs at that level or higher to be printed.