10 PostGIS Best Practices

PostGIS is a powerful open source spatial database that can be used to store, query, and analyze geospatial data. It is a popular choice for organizations that need to store and analyze large amounts of geospatial data.

However, it is important to use PostGIS correctly in order to get the most out of it. In this article, we will discuss 10 PostGIS best practices that will help you get the most out of your PostGIS database. We will discuss topics such as data types, indexing, and query optimization.

1. Create spatial indexes for faster query performance

Spatial indexes are data structures that store the spatial locations of features in a table. They allow PostGIS to quickly identify which records match a given query, as opposed to having to search through every record in the table. This makes queries much faster and more efficient.

Creating a spatial index is relatively simple. All you need to do is use the CREATE INDEX command with the GIST option. For example, if you have a table called “cities” with a column called “geom”, you can create an index like this:
CREATE INDEX cities_gist ON cities USING GIST (geom);

Once the index has been created, it will be used automatically whenever a query is run on the table. This means that any time you query the table for features within a certain area or distance, the query will be much faster than without the index.

2. Utilize the PostGIS raster functions to store and manipulate large datasets

PostGIS raster functions are designed to store and manipulate large datasets efficiently. This is because PostGIS stores the data in a tiled format, which allows for faster access of individual tiles when needed. Additionally, PostGIS can use spatial indexes to quickly locate specific tiles within the dataset.

The PostGIS raster functions also allow users to perform various operations on the data, such as resampling, reprojection, and mosaicking. These operations can be used to transform the data into different formats or resolutions, making it easier to work with. Furthermore, PostGIS provides tools for analyzing the data, such as calculating statistics, performing image processing, and creating visualizations.

3. Leverage ST_AsMVT to create vector tiles from PostGIS data

ST_AsMVT is a PostGIS function that allows users to create vector tiles from their PostGIS data. Vector tiles are small, lightweight files that can be used to quickly and efficiently render large amounts of geographic data on the web. By leveraging ST_AsMVT, users can take advantage of this technology without having to write any additional code or use external tools.

The process for creating vector tiles with ST_AsMVT is relatively straightforward. Users simply need to define the parameters of the tile they want to generate (such as the zoom level, bounding box, and layer name) and then call the ST_AsMVT function. The function will then return a binary representation of the requested tile which can be served directly to the client. This makes it easy to serve up dynamic maps in real-time without having to pre-generate all possible tiles.

4. Pre-aggregate data in PostGIS tables to reduce query time

Pre-aggregating data in PostGIS tables can help reduce query time by reducing the amount of data that needs to be processed. By pre-aggregating data, you are essentially creating a summary table with only the necessary information needed for your analysis. This means that when you run a query, it will only need to process the summarized data instead of all the original data points.

The way to pre-aggregate data in PostGIS is through the use of SQL queries. You can create a new table using an aggregate function such as SUM or AVG and then join this table to the original table on the desired columns. This will allow you to quickly summarize the data into a single table which can then be used for further analysis.

Additionally, you can also use PostGIS functions such as ST_Union and ST_ClusterIntersects to group together geometries that share similar characteristics. This can be useful if you want to analyze data at a higher level than individual features. For example, you could group together all buildings within a certain radius and then calculate the average height of those buildings.

5. Take advantage of PostGIS’s built-in geometry validation functions

PostGIS is a powerful spatial database that allows users to store and query geospatial data. It provides a wide range of functions for manipulating, analyzing, and validating geometry data. PostGIS’s built-in geometry validation functions are designed to ensure the accuracy and integrity of the data stored in the database. These functions can be used to check if the geometry data meets certain criteria such as being within a specified area or having a specific size.

Using these functions helps to prevent errors from occurring when working with geospatial data. For example, if an application requires a polygon to have four sides, then using the ST_IsValid function will help to ensure that only polygons with four sides are accepted into the database. This prevents any invalid data from entering the system and causing problems down the line.

Additionally, using PostGIS’s built-in geometry validation functions can improve performance by reducing the amount of time spent on manual checks. By automating the process, developers can focus their efforts on other tasks instead of manually checking each piece of data.

6. Make use of PostGIS’s powerful SQL/MM standard compliant functions

PostGIS is an open source extension to the PostgreSQL database that adds support for geographic objects. It allows users to store, query, and manipulate spatial data in a relational database. By utilizing SQL/MM standard compliant functions, PostGIS can be used to perform complex spatial analysis tasks with ease.

SQL/MM (Spatial) is an international standard for representing and manipulating spatial data in databases. It defines a set of functions and operators that allow users to work with spatial data stored in a database. These functions are designed to make it easier to work with spatial data by providing a consistent interface across different databases.

Using these functions makes it possible to write queries that are portable across different databases. This means that if you need to switch from one database to another, your queries will still work as long as they use the same SQL/MM functions. Additionally, using SQL/MM functions ensures that your queries are optimized for performance since the underlying implementation of the function is already optimized for the specific database.

7. When possible, utilize PostGIS’s native geospatial types instead of text or other formats

PostGIS is a powerful geospatial database that allows users to store, query, and manipulate spatial data. It provides native support for the most common geospatial types such as points, lines, polygons, and rasters. By using PostGIS’s native geospatial types instead of text or other formats, users can take advantage of PostGIS’s built-in functions and operators which are optimized for working with these types. This makes it easier to perform complex queries and analysis on the data.

Using PostGIS’s native geospatial types also helps improve performance when querying large datasets. Since PostGIS is designed to work with these types, it can quickly process them without having to convert them from another format. Additionally, since PostGIS stores the data in its native format, there is no need to parse the data into a different format before performing operations on it. This reduces the amount of time needed to process the data and improves overall performance.

8. Consider using a PostGIS extension such as pgRouting for routing applications

pgRouting is an open source extension for PostGIS that provides a set of functions and tools to solve routing problems. It allows users to find the shortest path between two points, calculate the cost of travel along a route, and even plan routes with multiple stops. pgRouting also supports advanced features such as network analysis, vehicle routing, and turn restrictions.

Using pgRouting in conjunction with PostGIS makes it easier to store, query, and analyze spatial data. This combination enables users to quickly create complex queries and perform sophisticated analyses on their data. For example, they can easily calculate the distance between two points or determine the best route from one point to another. Additionally, pgRouting’s support for network analysis means users can identify areas of high traffic density or locate optimal locations for new facilities.

9. Store PostGIS data in a schema separate from non-spatial data

When using PostGIS, it is important to keep spatial and non-spatial data separate. This helps ensure that the database remains organized and efficient. By keeping the two types of data in different schemas, queries can be optimized for each type of data. For example, a query on spatial data may require more complex calculations than a query on non-spatial data, so having them in separate schemas allows the query optimizer to optimize the query accordingly.

It also makes it easier to manage permissions. When all the spatial data is stored in one schema, it is much simpler to grant or revoke access to that schema rather than managing individual tables. Additionally, if there are multiple users accessing the same database, they can have their own schemas with their own set of permissions.

Creating a separate schema for PostGIS data is relatively simple. All you need to do is create a new schema in the database and then move the relevant tables into it. Once the tables are moved, any existing views or functions that reference those tables will need to be updated to use the new schema name. Finally, any users who need access to the PostGIS data should be granted permission to the new schema.

10. Utilize stored procedures for complex queries

Stored procedures are pre-compiled SQL statements that can be called from within a database. This means they can be reused and shared, making them an efficient way to manage complex queries. Stored procedures also provide better performance than running the same query multiple times, as the code is already compiled and optimized for execution.

Using stored procedures with PostGIS allows users to take advantage of its powerful spatial functions. For example, if you need to calculate the distance between two points, you can create a stored procedure that uses the ST_Distance() function. This will save time and resources compared to writing out the entire query each time it needs to be run.

Additionally, stored procedures can help improve security by allowing only certain users access to specific queries. This prevents unauthorized users from accessing sensitive data or executing potentially dangerous commands.