Debugging: LATERAL query in PostgreSQL - postgresql

Question

SELECT
cu.user_id,
cu.gender,
CASE WHEN cu.looking_for_gender = cu.gender THEN 1 ELSE 0 END AS
sexual_orientation,
os_name,
ROUND((DATE(NOW()) - cu.birthdate)/365.25) AS user_age,
SUM(dsb.likes) AS likes,
SUM(dsb.dislikes) AS dislikes,
SUM(dsb.blocks) AS blocks,
SUM(dsb.matches) AS matches,
SUM(dsb.received_likes) AS received_likes,
SUM(dsb.received_dislikes) AS received_dislikes,
SUM(dsb.received_blocks) AS received_blocks,
CASE WHEN cu.status = 'default' THEN 1 ELSE 0 END AS recall_case,
CASE WHEN cu.status = 'default' THEN extract(epoch from
cu.last_activity - cu.updated_time)/86400 ELSE 0 END AS
recall_retention
FROM ( SELECT stats.core_users cu
LEFT JOIN yay.daily_swipes_by_users dsb ON (dsb.user_id = cu.user_id)
WHERE cu.user_id = '1' GROUP BY 1) e1
LEFT JOIN LATERAL (SELECT cd.os_name FROM stats.core_devices cd WHERE
e1.user_id = cd.user_id ORDER BY cd.updated_time DESC LIMIT 1) e2
ON TRUE;
Current Error Code:
ERROR: syntax error at or near "LEFT"
LINE 18: LEFT JOIN yay.daily_swipes_by_users dsb ON (dsb.user_id = cu...
^

Answer 1

The supplied query would fail in many ways, the following might work I hope, but as you can see this drops a great deal of other columns in the process
SELECT
e1.user_id
, e1.cu
, e2.os_name
FROM (
SELECT stats.core_users cu, cu.user_id
LEFT JOIN yay.daily_swipes_by_users dsb ON (dsb.user_id = cu.user_id)
WHERE cu.user_id = '1'
GROUP BY stats.core_users cu, cu.user_id
) e1
LEFT JOIN LATERAL(
SELECT cd.os_name
FROM stats.core_devices cd
WHERE e1.user_id = cd.user_id
ORDER BY cd.updated_time DESC
LIMIT 1) e2 ON TRUE
;

Answer 2

SELECT
cu.user_id,
cu.gender,
CASE WHEN cu.looking_for_gender = cu.gender THEN 1 ELSE 0 END AS sexual_orientation,
e2.os_name,
ROUND((DATE(NOW()) - cu.birthdate)/365.25) AS user_age,
CASE WHEN cu.status = 'default' THEN 1 ELSE 0 END AS recall_case,
CASE WHEN cu.status = 'default' THEN extract(epoch from cu.last_activity - cu.updated_time)/86400 ELSE 0 END AS recall_retention,
SUM(dsb.likes) AS likes,
SUM(dsb.dislikes) AS dislikes,
SUM(dsb.blocks) AS blocks,
SUM(dsb.matches) AS matches,
SUM(dsb.received_likes) AS received_likes,
SUM(dsb.received_dislikes) AS received_dislikes,
SUM(dsb.received_blocks) AS received_blocks
FROM
stats.core_users cu
LEFT JOIN yay.daily_swipes_by_users dsb ON (dsb.user_id = cu.user_id)
LEFT JOIN LATERAL (SELECT cd.os_name FROM stats.core_devices cd WHERE cu.user_id = cd.user_id ORDER BY cd.updated_time DESC LIMIT 1) e2
ON TRUE
WHERE cu.user_id = '1'
GROUP BY 1,2,3,4,5,6,7
;
This works.