利用自定义函数输出各种类型数据的luadbi驱动ducktpch.lua
lua
DBI = require "DBI"
dbd, err = DBI.Connect( 'DuckDB', 'tpch_duckdb', 'dbuser', 'password' )
assert(dbd, err)
dbd:autocommit(true)
statement = assert(dbd:prepare( "SELECT * from lineitem" ))
statement:execute()
tabcol={}
tabval={}
i=1
for row in statement:rows(true) do
if (i==1)
then
for key, value in pairs(row) do tabcol[i]=key i=i+1 end
headerstring=table.concat(tabcol, ",")
print(headerstring)
end
for key, value in pairs(tabcol)do tabval[key]=row[tabcol[key]] end
rowstring=table.concat(tabval, ",")
print(rowstring)
end利用duckdb C API函数duckdb_value_varchar输出各种类型数据的字符串的luasql驱动ducktpch2.lua
lua
driver = require"luasql.duckdb"
env = assert (driver.duckdb())
con = assert (env:connect("tpch_duckdb"))
cur = assert (con:execute"SELECT * from lineitem")
row = cur:fetch ({}, "a") -- the rows will be indexed by field names
tabcol={}
i=1
for key, value in pairs(row) do tabcol[i]=key i=i+1 end
headerstring=table.concat(tabcol, ",")
print(headerstring)
tabval={}
while row do
for key, value in pairs(tabcol)do tabval[key]=row[tabcol[key]] end
rowstring=table.concat(tabval, ",")
print(rowstring)
row = cur:fetch (row, "a") -- reusing the table of results
end执行结果
root@66d4e20ec1d7:/par/luadbi# lua ../ducktpch.lua
l_linestatus,l_linenumber,l_comment,l_tax,l_commitdate,l_extendedprice,l_shipdate,l_suppkey,l_partkey,l_receiptdate,l_shipmode,l_returnflag,l_discount,l_shipinstruct,l_quantity,l_orderkey
O,1,to beans x-ray carefull,0.02,1996-02-12,24386.67,1996-03-13,785,15519,1996-03-22,TRUCK,N,0.04,DELIVER IN PERSON,17.00,1
root@66d4e20ec1d7:/par/luadbi# time lua ../ducktpch.lua >/dev/null
real 0m7.979s
user 0m7.756s
sys 0m0.352s
root@66d4e20ec1d7:/par/luadbi# time lua ../ducktpch2.lua >/dev/null
real 0m9.301s
user 0m8.424s
sys 0m1.140s
root@66d4e20ec1d7:/par/luadbi# time lua ../ducktpch.lua >/tmp/1.csv
real 0m9.137s
user 0m8.196s
sys 0m1.096s
root@66d4e20ec1d7:/par/luadbi# time lua ../ducktpch2.lua > /tmp/2.csv
real 0m9.905s
user 0m8.636s
sys 0m1.296s
ls -l /tmp/1.csv /tmp/2.csv
-rw-r--r-- 1 root root 75524898 Nov 3 14:59 /tmp/1.csv
-rw-r--r-- 1 root root 75448328 Nov 3 15:00 /tmp/2.csv两种驱动没有明显差异。
如果把print到控制台再重定向改为直接对文件写操作，则性能提升，不过这与duckdb驱动无关。
lua
-- 以附加的方式打开只写文件
file = io.open("testlua.csv", "a")
-- 设置默认输出文件为 test.lua
io.output(file)
io.write(headerstring)
io.write("\n")
while row do
for key, value in pairs(tabcol)do tabval[key]=row[tabcol[key]] end
local rowstring=table.concat(tabval, ",")
-- print(rowstring)
io.write(rowstring)
io.write("\n")
row = cur:fetch (row, "a") -- reusing the table of results
end
-- 关闭打开的文件
io.close(file)排除print慢的操作，都用直接写文件来对比，还是平局。
root@66d4e20ec1d7:/par/luadbi# time lua ../ducktpchf.lua
real 0m8.632s
user 0m8.096s
sys 0m0.136s
root@66d4e20ec1d7:/par/luadbi# time lua ../ducktpch2f.lua
real 0m7.259s
user 0m7.068s
sys 0m0.348s完整直接写文件脚本如下
luadbi ducktpchf.lua
lua
DBI = require "DBI"
dbd, err = DBI.Connect( 'DuckDB', 'tpch_duckdb', 'dbuser', 'password' )
assert(dbd, err)
dbd:autocommit(true)
statement = assert(dbd:prepare( "SELECT * from lineitem" ))
statement:execute()
tabcol={}
tabval={}
i=1
-- 以附加的方式打开只写文件
file = io.open("testlua.csv", "w")
-- 设置默认输出文件为 test.lua
io.output(file)
for row in statement:rows(true) do
if (i==1)
then
for key, value in pairs(row) do tabcol[i]=key i=i+1 end
headerstring=table.concat(tabcol, ",")
print(headerstring)
io.write(headerstring)
io.write("\n")
end
for key, value in pairs(tabcol)do tabval[key]=row[tabcol[key]] end
rowstring=table.concat(tabval, ",")
-- print(rowstring)
io.write(rowstring)
io.write("\n")
end
-- 关闭打开的文件
io.close(file)luadbi ducktpch2f.lua
lua
driver = require"luasql.duckdb"
env = assert (driver.duckdb())
con = assert (env:connect("tpch_duckdb"))
cur = assert (con:execute"SELECT * from lineitem")
local row = cur:fetch ({}, "n") -- the rows will be indexed by field number
local tabcol={}
i=1
for key, value in pairs(row) do tabcol[i]=key i=i+1 end
local headerstring=table.concat(tabcol, ",")
print(headerstring)
local tabval={}
-- 以附加的方式打开只写文件
file = io.open("testlua.csv", "w")
-- 设置默认输出文件为 test.lua
io.output(file)
io.write(headerstring)
io.write("\n")
while row do
for key, value in pairs(tabcol)do tabval[key]=row[tabcol[key]] end
local rowstring=table.concat(tabval, ",")
-- print(rowstring)
io.write(rowstring)
io.write("\n")
row = cur:fetch (row, "n") -- reusing the table of results
end
-- 关闭打开的文件
io.close(file)