I do not see tables structure, indexes, the view definition, sample data,
expected results...

Here is a quick attempt to improve this. Check the you have correct indexes
on join and filter columns where applicable.

In the main query below I removed two of the functions and used sub-queries.
Not sure that will help but was easier for me to see the logic. Changed the
main function to be table valued (you can go a step further here to make it
table valued for all users and join by user, I did not want to dig into the
logic there) so there will be no two calls in SELECT and WHERE, and some
other cosmetic changes. Note that this is untested.

SELECT U.UserID,
U.FirstName + ' ' + U.LastName AS 'Name',
P.PropertyValue AS Location,
N.headline AS Headline,
I.industryName AS Industry,
professionalInfo.summary AS Summary,
professionalInfo.interests,
(SELECT COUNT(*)
FROM network AS N
WHERE (N.memberId = U.UserID
OR N.friendId = U.UserID)
AND status = 1) AS Connections,
(SELECT COUNT(*)
FROM endorsements AS E
WHERE E.memberId = U.UserID
AND status = 'Accepted') AS Recommendations,
F.generation AS Degree
FROM Users AS U
JOIN UserProfile AS P
ON U.UserID = P.UserID
JOIN professionalInfo AS N
ON U.UserID = N.memberId
JOIN industries AS I
ON N.primaryIndustry = I.industryId
CROSS APPLY dbo.fnCommonFriendsStep(U.UserID, 36) AS F
WHERE EXISTS (SELECT *
FROM vw_search AS S
WHERE S.UserID = U.UserID)
AND P.PropertyDefinitionID = 29
AND F.generation >= 0
ORDER By Degree ASC



And here is the changed function:

CREATE FUNCTION dbo.fnCommonFriendsStep
(@member INT, @friend INT)
RETURNS @FriendsDegree
TABLE (generation INT DEFAULT 0)
AS
BEGIN

INSERT INTO @FriendsDegree DEFAULT VALUES

IF @member = @friend
RETURN

DECLARE @Friends TABLE (generation INT, p INT)
DECLARE @generation INT

SET @generation = 0

INSERT @Friends (generation, p)
SELECT 0, memberId
FROM Network
WHERE friendId = @member
UNION
SELECT 0, friendId
FROM Network
WHERE memberId = @member

WHILE NOT EXISTS (SELECT 1 FROM @Friends WHERE p = @friend)
AND @generation >= 0
BEGIN
SELECT @generation = @generation + 1

INSERT @Friends (generation, p)
SELECT @generation, memberId
FROM Network AS N
WHERE EXISTS (SELECT *
FROM @Friends AS F
WHERE N.friendid = F.p
AND F.generation = @generation - 1)
AND NOT EXISTS (SELECT *
FROM @Friends AS F
WHERE N.memberid = F.p)
UNION
SELECT @generation, friendId
FROM Network AS N
WHERE EXISTS (SELECT *
FROM @Friends AS F
WHERE N.memberid = F.p
AND F.generation = @generation - 1)
AND NOT EXISTS (SELECT *
FROM @Friends AS F
WHERE N.friendid = F.p)

IF @@ROWCOUNT = 0
SELECT @generation = -2
END

UPDATE @FriendsDegree
SET generation = @generation + 1

RETURN
END



HTH,

Plamen Ratchev
http://www.SQLStudio.com