added tests

README.md

@@ -234,6 +234,9 @@ from the `txn` table when `commit()` returned an error is undefined.
 Return all keys `>= start` and starts with `prefix`. If `db` is omitted,
 it defaults to `"_default"`.
 
+If `page_size` is specified, up to `page_size` results will be returned. However,
+`page_size` can not be set to less than `2` due to internal implementation limitations.
+
 The return value of this function is a table `res` where `res[1].key` and `res[1].value`
 corresponds to the first key and value, `res[2].key` and `res[2].value` corresponds to the
 second and etc. If no keys matched the provided criteria, then an empty table will be
@@ -246,6 +249,9 @@ matching the `prefix` is available.
 
 In case of errors, `nil` and an string describing the reason of the failure will be returned.
 
+This is a low level function, most of the use case should instead use the higher level
+[lmdb.prefix](#prefix) iterator instead.
+
 [Back to TOC](#table-of-contents)
 
 ## Directives

lib/resty/lmdb/prefix.lua

@@ -31,6 +31,8 @@ function _M.page(start, prefix, db, page_size)
         page_size = DEFAULT_OPS_SIZE
     end
 
+    assert(page_size >= 2, "'page_size' can not be less than 2")
+
     local value_buf_size = get_string_buf_size()
     local ops = ffi_new("ngx_lua_resty_lmdb_operation_t[?]", page_size)
 

t/10-prefix.t

@@ -214,3 +214,114 @@ done
 [error]
 [warn]
 [crit]
+
+
+
+=== TEST 6: prefix.page() operation
+--- http_config eval: $::HttpConfig
+--- main_config eval: $::MainConfig
+--- config
+    location = /t {
+        content_by_lua_block {
+            local l = require("resty.lmdb")
+
+            ngx.say(l.db_drop(true))
+            ngx.say(l.set("test", "value"))
+            ngx.say(l.set("test1", "value1"))
+            ngx.say(l.set("test2", "value2"))
+            ngx.say(l.set("test3", "value3"))
+            ngx.say(l.set("u", "value4"))
+            ngx.say(l.set("u1", "value5"))
+
+            local p = require("resty.lmdb.prefix")
+
+            local res, err = p.page("test", "test")
+            if not res then
+                ngx.say("page errored: ", err)
+            end
+
+            for _, pair in ipairs(res) do
+                ngx.say("key: ", pair.key, " value: ", pair.value)
+            end
+        }
+    }
+--- request
+GET /t
+--- response_body
+true
+true
+true
+true
+true
+true
+true
+key: test value: value
+key: test1 value: value1
+key: test2 value: value2
+key: test3 value: value3
+--- no_error_log
+[error]
+[warn]
+[crit]
+
+
+
+=== TEST 7: prefix.page() operation with custom page size
+--- http_config eval: $::HttpConfig
+--- main_config eval: $::MainConfig
+--- config
+    location = /t {
+        content_by_lua_block {
+            local l = require("resty.lmdb")
+
+            ngx.say(l.db_drop(true))
+            ngx.say(l.set("test", "value"))
+            ngx.say(l.set("test1", "value1"))
+            ngx.say(l.set("test2", "value2"))
+            ngx.say(l.set("test3", "value3"))
+            ngx.say(l.set("u", "value4"))
+            ngx.say(l.set("u1", "value5"))
+
+            local p = require("resty.lmdb.prefix")
+
+            local res, err = p.page("test", "test", nil, 2)
+            if not res then
+                ngx.say("page errored: ", err)
+            end
+
+            ngx.say("FIRST PAGE")
+            for _, pair in ipairs(res) do
+                ngx.say("key: ", pair.key, " value: ", pair.value)
+            end
+
+            res, err = p.page("test1\x00", "test", nil, 2)
+            if not res then
+                ngx.say("page errored: ", err)
+            end
+
+            ngx.say("SECOND PAGE")
+            for _, pair in ipairs(res) do
+                ngx.say("key: ", pair.key, " value: ", pair.value)
+            end
+        }
+    }
+--- request
+GET /t
+--- response_body
+true
+true
+true
+true
+true
+true
+true
+FIRST PAGE
+key: test value: value
+key: test1 value: value1
+SECOND PAGE
+key: test2 value: value2
+key: test3 value: value3
+--- no_error_log
+[error]
+[warn]
+[crit]