ST_MemUnion — Same as ST_Union, only memory-friendly (uses less memory and more processor time).
geometry ST_MemUnion(geometry set geomfield);
Some useful description here.
| ![[Note]](images/note.png) | |
| Same as ST_Union, only memory-friendly (uses less memory and more processor time). This aggregate function works by unioning the geometries one at a time to previous result as opposed to ST_Union aggregate which first creates an array and then unions | 
 This function supports 3d and will not drop the z-index.
 This function supports 3d and will not drop the z-index.