accessing query responses with lua-resty-mysql

davidmuscut · 2015-11-02T22:16:06+00:00

Hello! On Mon, Nov 2, 2015 at 11:49 AM, MELWIN JOSE wrote: > I want a particular function to be called every 15seconds (i.e I need to > setup a timer)...

accessing query responses with lua-resty-mysql

davidmuscut

The lua-resty-mysql documentation uses cjson.encode() to demonstrate how to access a mysql select query response. I want to access the "id" column from my response but get error messages. For example, when I cjson.encode() the response to ngx.log() I get (as expected):
[{"weight":2453,"id":"84200"}]

but when I try to access the "id" column from the results table via the following code:

local Query = "SELECT id FROM docs WHERE MATCH(" .. Quoted_Email .. ")"
local Res, Err, Errno, Sqlstate = db:query(Query, 10)
ngx.log(ngx.ERR, "DocID: ", Res["id"])

I get:
DocID: nil

When I try looping through the table with:
for key,value in pairs(Res) do ngx.log(ngx.ERR, key,value) end

I get:
bad argument #2 to 'log' (string, number, boolean, or nil expected, got table)
stack traceback: ...

I verified that Res is a table, how can I access the id column without json encoding the response?

thanks!

- D

davidmuscut

On Monday, November 2, 2015 at 4:16:06 PM UTC+2, david...@gmail.com wrote:

I verified that Res is a table, how can I access the id column without json encoding the response?

Problem solved via:

local counter = 1
while counter <= #res do
ngx.log(ngx.ERR, "DocID: ", Res[counter]["id"])
counter = counter + 1
end

me_0943

With your first example, it should work if you change it to:

for key,value in pairs(Res) do ngx.log(ngx.ERR, key,value.id) end

'value' in your first example is actually a table representing one of the rows returned by your mysql query, with the column name as the keys.

Since lua doesn't know how you want it to print a table, it warns you that you provided a table and not a string/number/etc; the example in lua-resty-mysql is just using cjson as an easy way to print out a table in a readable way.

Hope that helped!

Cheers,

Chris

https://groups.google.com/forum/#!topic/openresty-en/-WpGNg7NVi0

On Monday, November 2, 2015 at 8:46:11 PM UTC, david...@gmail.com wrote:

On Monday, November 2, 2015 at 4:16:06 PM UTC+2, david...@gmail.com wrote:

I verified that Res is a table, how can I access the id column without json encoding the response?

Problem solved via:

local counter = 1
while counter <= #res do
ngx.log(ngx.ERR, "DocID: ", Res[counter]["id"])
counter = counter + 1
end