Execute and load SQL processing algorithm fails if statement includes semi colon

[timlinux]

Environment: QGIS 3.4.8 on macOS

It is common practice to include a semi-colon at the end of an SQL statement. However when doing this in the 'Execute and load SQL' processing algorithm, the algorithm fails with a cryptic message:

Loading resulting layers
Algorithm 'PostgreSQL execute and load SQL' finished
Processing algorithm…
Algorithm 'PostgreSQL execute and load SQL' starting…
Input parameters:
{ 'DATABASE' : 'Dominica on Postgres.app', 'GEOMETRY_FIELD' : 'geom', 'ID_FIELD' : 'id', 'SQL' : 'select id, geom, distance from potential_site_points;' }

Traceback (most recent call last):
File "/Applications/QGIS3.4.app/Contents/MacOS/../Resources/python/plugins/processing/algs/qgis/PostGISExecuteAndLoadSQL.py", line 114, in processAlgorithm
Please check the PostGIS log for error messages."""))
_core.QgsProcessingException: This layer is invalid!
Please check the PostGIS log for error messages.

Execution failed after 0.07 seconds

Loading resulting layers
Algorithm 'PostgreSQL execute and load SQL' finished
Processing algorithm…
Algorithm 'PostgreSQL execute and load SQL' starting…
Input parameters:
{ 'DATABASE' : 'Dominica on Postgres.app', 'GEOMETRY_FIELD' : 'geom', 'ID_FIELD' : 'id', 'SQL' : 'select id, geom, distance from potential_site_points' }

Execution completed in 0.11 seconds
Results:
{'OUTPUT': 'layername_4c541080_d310_497c_ac7d_3bdf7bb357fd'}

Loading resulting layers
Algorithm 'PostgreSQL execute and load SQL' finished

I enabled logging in my PostGIS instance and saw the issue was caused by a stray semi-colon:

2019-06-16 17:27:59.880 WEST [15809] STATEMENT:  
SELECT * FROM (select id, geom, distance from potential_site_points;) AS "subQuery_0" LIMIT 1

Using the tool again with no semi-colon allows the statement to run successfully:

Algorithm 'PostgreSQL execute and load SQL' starting…
Input parameters:
{ 'DATABASE' : 'Dominica on Postgres.app', 'GEOMETRY_FIELD' : 'geom', 'ID_FIELD' : 'id', 'SQL' : 'select id, geom, distance from potential_site_points' }

Execution completed in 0.11 seconds
Results:
{'OUTPUT': 'layername_4c541080_d310_497c_ac7d_3bdf7bb357fd'}

Loading resulting layers
Algorithm 'PostgreSQL execute and load SQL' finished
Processing algorithm…
Algorithm 'PostgreSQL execute and load SQL' starting…
Input parameters:
{ 'DATABASE' : 'Dominica on Postgres.app', 'GEOMETRY_FIELD' : 'geom', 'ID_FIELD' : 'id', 'SQL' : 'select id, geom, distance from potential_site_points' }

Execution completed in 0.10 seconds
Results:
{'OUTPUT': 'layername_88c8b485_7f29_44e9_ab2d_a62a22d5ab63'}

Loading resulting layers
Algorithm 'PostgreSQL execute and load SQL' finished

[timlinux]

Note also that the 'PostgreSQL Execute SQL' algorithm works with a semi colon at the end of the statement.

[timlinux]

Thanks @alexbruy !