Lua

DynamoDB - Query

See more Amazon DynamoDB Examples

The Query operation finds items based on primary key values. You can query any table or secondary index that has a composite primary key (a partition key and a sort key). Lua

local chilkat = require("chilkat")

local rest = chilkat.Rest.new()

-- Implements the following CURL command:

-- curl -X POST https://dynamodb.us-west-2.amazonaws.com/ \
--   -H "Accept-Encoding: identity" \
--   -H "Content-Type: application/x-amz-json-1.0" \
--   -H "Authorization: AWS4-HMAC-SHA256 Credential=<Credential>, SignedHeaders=<Headers>, Signature=<Signature>" \
--   -H "X-Amz-Date: <Date>" \
--   -H "X-Amz-Target: DynamoDB_20120810.Query" \
--   -d '{
--     "TableName": "Reply",
--     "IndexName": "PostedBy-Index",
--     "Limit": 3,
--     "ConsistentRead": true,
--     "ProjectionExpression": "Id, PostedBy, ReplyDateTime",
--     "KeyConditionExpression": "Id = :v1 AND PostedBy BETWEEN :v2a AND :v2b",
--     "ExpressionAttributeValues": {
--         ":v1": {"S": "Amazon DynamoDB#DynamoDB Thread 1"},
--         ":v2a": {"S": "User A"},
--         ":v2b": {"S": "User C"}
--     },
--     "ReturnConsumedCapacity": "TOTAL"
-- }'

-- Use the following online tool to generate REST code from a CURL command
-- Convert a cURL Command to REST Source Code

local authAws = chilkat.AuthAws.new()
authAws.access_key = "AWS_ACCESS_KEY"
authAws.secret_key = "AWS_SECRET_KEY"
-- Don't forget to change the region to your particular region. (Also make the same change in the call to Connect below.)
authAws.region = "us-west-2"
authAws.service_name = "dynamodb"
-- SetAuthAws causes Chilkat to automatically add the following headers: Authorization, X-Amz-Date
rest:set_auth_aws(authAws)

-- URL: https://dynamodb.us-west-2.amazonaws.com/
local bTls = true
local port = 443
local bAutoReconnect = true
local success = rest:connect("dynamodb.us-west-2.amazonaws.com", port, bTls, bAutoReconnect)
if not success then
    print("ConnectFailReason: " .. rest.connect_fail_reason)
    print(rest.last_error_text)
    return
end

-- Note: The above code does not need to be repeatedly called for each REST request.
-- The rest object can be setup once, and then many requests can be sent.  Chilkat will automatically
-- reconnect within a FullRequest* method as needed.  It is only the very first connection that is explicitly
-- made via the Connect method.

-- Use this online tool to generate code from sample JSON:
-- Generate Code to Create JSON

-- The following JSON is sent in the request body.

-- {
--   "TableName": "Reply",
--   "IndexName": "PostedBy-Index",
--   "Limit": 3,
--   "ConsistentRead": true,
--   "ProjectionExpression": "Id, PostedBy, ReplyDateTime",
--   "KeyConditionExpression": "Id = :v1 AND PostedBy BETWEEN :v2a AND :v2b",
--   "ExpressionAttributeValues": {
--     ":v1": {
--       "S": "Amazon DynamoDB#DynamoDB Thread 1"
--     },
--     ":v2a": {
--       "S": "User A"
--     },
--     ":v2b": {
--       "S": "User C"
--     }
--   },
--   "ReturnConsumedCapacity": "TOTAL"
-- }

local json = chilkat.JsonObject.new()
json:update_string("TableName", "Reply")
json:update_string("IndexName", "PostedBy-Index")
json:update_int("Limit", 3)
json:update_bool("ConsistentRead", true)
json:update_string("ProjectionExpression", "Id, PostedBy, ReplyDateTime")
json:update_string("KeyConditionExpression", "Id = :v1 AND PostedBy BETWEEN :v2a AND :v2b")
json:update_string("ExpressionAttributeValues.:v1.S", "Amazon DynamoDB#DynamoDB Thread 1")
json:update_string("ExpressionAttributeValues.:v2a.S", "User A")
json:update_string("ExpressionAttributeValues.:v2b.S", "User C")
json:update_string("ReturnConsumedCapacity", "TOTAL")

rest:add_header("Content-Type", "application/x-amz-json-1.0")
rest:add_header("X-Amz-Target", "DynamoDB_20120810.Query")
rest:add_header("Accept-Encoding", "identity")

local sbRequestBody = chilkat.StringBuilder.new()
json:emit_sb(sbRequestBody)
local sbResponseBody = chilkat.StringBuilder.new()
success = rest:full_request_sb("POST", "/", sbRequestBody, sbResponseBody)
if not success then
    print(rest.last_error_text)
    return
end

local respStatusCode = rest.response_status_code
print("response status code = " .. respStatusCode)
if respStatusCode >= 400 then
    print("Response Status Code = " .. respStatusCode)
    print("Response Header:")
    print(rest.response_header)
    print("Response Body:")
    print(sbResponseBody:get_as_string())
    return
end

local jsonResponse = chilkat.JsonObject.new()
jsonResponse:load_sb(sbResponseBody)

jsonResponse.emit_compact = false
print(jsonResponse:emit())

-- Sample JSON response:
-- (Sample code for parsing the JSON response is shown below)

-- {
--   "ConsumedCapacity": {
--     "CapacityUnits": 1,
--     "TableName": "Reply"
--   },
--   "Count": 2,
--   "Items": [
--     {
--       "ReplyDateTime": {
--         "S": "2015-02-18T20:27:36.165Z"
--       },
--       "PostedBy": {
--         "S": "User A"
--       },
--       "Id": {
--         "S": "Amazon DynamoDB#DynamoDB Thread 1"
--       }
--     },
--     {
--       "ReplyDateTime": {
--         "S": "2015-02-25T20:27:36.165Z"
--       },
--       "PostedBy": {
--         "S": "User B"
--       },
--       "Id": {
--         "S": "Amazon DynamoDB#DynamoDB Thread 1"
--       }
--     }
--   ],
--   "ScannedCount": 2
-- }

-- Sample code for parsing the JSON response...
-- Use the following online tool to generate parsing code from sample JSON:
-- Generate Parsing Code from JSON

local ReplyDateTimeS = ""
local PostedByS = ""
local IdS = ""

local ConsumedCapacityCapacityUnits = jsonResponse:int_of("ConsumedCapacity.CapacityUnits")
local ConsumedCapacityTableName = jsonResponse:string_of("ConsumedCapacity.TableName")
local Count = jsonResponse:int_of("Count")
local ScannedCount = jsonResponse:int_of("ScannedCount")
local i = 0
local count_i = jsonResponse:size_of_array("Items")
while i < count_i do
    jsonResponse.i = i
    ReplyDateTimeS = jsonResponse:string_of("Items[i].ReplyDateTime.S")
    PostedByS = jsonResponse:string_of("Items[i].PostedBy.S")
    IdS = jsonResponse:string_of("Items[i].Id.S")
    i = i + 1
end