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gofdw.go
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gofdw.go
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package main
/*
#cgo CFLAGS: -I/usr/include/postgresql/9.5/server
#cgo LDFLAGS: -Wl,-unresolved-symbols=ignore-all
#include "postgres.h"
#include "access/reloptions.h"
#include "commands/defrem.h"
#include "foreign/fdwapi.h"
#include "foreign/foreign.h"
#include "optimizer/cost.h"
#include "optimizer/pathnode.h"
#include "optimizer/planmain.h"
#include "optimizer/restrictinfo.h"
#include "utils/rel.h"
#include "utils/builtins.h"
*/
import "C"
import (
"bufio"
"bytes"
"encoding/json"
"io"
"log"
"os/exec"
"reflect"
"unsafe"
)
//export FdwInit
func FdwInit() {
log.Print("FdwInit")
}
//export FdwValidator
func FdwValidator(options *C.List, catalog C.Oid) {
iterateList(options, func(ptr unsafe.Pointer) {
elem := (*C.DefElem)(ptr)
name := C.GoString(elem.defname)
value := C.GoString(C.defGetString(elem))
log.Print("option ", name, "=", value)
})
}
type Cond interface{}
type PeriodCond struct {
day int
op byte
}
type GrepCond struct {
field string
value string
}
type PlanState struct {
conds []Cond
meta map[string]int
}
//export FdwGetRelSize
func FdwGetRelSize(root *C.PlannerInfo, baseRel *C.RelOptInfo, tableId C.Oid) {
state := &PlanState{
conds: []Cond{},
}
baseRel.fdw_private = cRetain(state)
iterateList(baseRel.baserestrictinfo, func(ptr unsafe.Pointer) {
clause := ((*C.RestrictInfo)(ptr)).clause
tag := getNodeTag(unsafe.Pointer(clause))
if tag == C.T_OpExpr {
log.Print("OP EXPR!!")
} else {
log.Print("other expr ", int(tag))
}
state.conds = append(state.conds, &PeriodCond{day: 1, op: '>'})
})
// todo:
// - read $dir/meta
// - sum tupleCounts
tupleCount := 0
selectivity := float64(C.clauselist_selectivity(root, baseRel.baserestrictinfo, 0, C.JOIN_INNER, nil))
baseRel.rows = C.clamp_row_est(C.double(float64(tupleCount) * selectivity))
log.Print("FdwGetRelSize ", " rows=", int(baseRel.rows))
// todo: baseRel.width
}
//export FdwGetPaths
func FdwGetPaths(root *C.PlannerInfo, baseRel *C.RelOptInfo, tableId C.Oid) {
state := cRetained(baseRel.fdw_private).(*PlanState)
log.Print("FdwGetPaths ctx=", state)
// add a single access path
startupCost := float64(baseRel.baserestrictcost.startup)
totalCost := startupCost + float64(C.cpu_tuple_cost*baseRel.rows)
foreignPath := C.create_foreignscan_path(root, baseRel, baseRel.rows, C.Cost(startupCost), C.Cost(totalCost), nil, nil, nil, nil)
C.add_path(baseRel, &foreignPath.path)
}
//export FdwGetPlan
func FdwGetPlan(root *C.PlannerInfo, baseRel *C.RelOptInfo, tableId C.Oid, bestPath *C.ForeignPath, tlist *C.List, scanClauses *C.List, outerPlan *C.Plan) *C.ForeignScan {
state := cRetained(baseRel.fdw_private).(*PlanState)
log.Print("FdwGetPlan ctx=", state)
scanClauses = C.extract_actual_clauses(scanClauses, C.false)
baseRel.fdw_private = nil
cRelease(state)
// pass data down to FdwBegin: wrap it in a *C.List
// var private *C.List
// private = C.lappend(private, baseRel.fdw_private)
return C.make_foreignscan(tlist, scanClauses, baseRel.relid, scanClauses, nil, nil, nil, outerPlan)
}
type ExecState struct {
dir string
files []string
cmds []*exec.Cmd
out *bufio.Reader
count int
}
//export FdwBegin
func FdwBegin(node *C.ForeignScanState, eflags C.int) {
rel := node.ss.ss_currentRelation // *C.RelationData
tableId := rel.rd_id
state := &ExecState{}
node.fdw_state = cRetain(state)
// node.fdw_state = C.list_nth(fscan.fdw_private, 0) // copy context pointer from fscan.fdw_private to node.fdw_state
state.dir = getDir(tableId)
// todo: check *Plan node.ss.ps.plan is indeed of type ForeignScan?
fscan := (*C.ForeignScan)(unsafe.Pointer(node.ss.ps.plan))
iterateList(fscan.fdw_exprs, func(ptr unsafe.Pointer) {
expr := (*C.Expr)(ptr)
log.Print(" expr!", int(expr._type), " ", C.T_OpExpr)
})
tupDesc := rel.rd_att
n := int(tupDesc.natts)
log.Print(" n=", n)
cmd := exec.Command("/bin/cat", state.dir+"/data100m.json")
log.Print(" cmd=", cmd)
state.cmds = []*exec.Cmd{}
for {
state.cmds = append(state.cmds, cmd)
r, err := cmd.StdoutPipe()
if err == nil {
log.Print("start")
err = cmd.Start()
}
if err != nil {
log.Print(err)
return
}
if len(state.cmds) == 1 {
state.out = bufio.NewReader(r)
break
}
cmd = exec.Command("/bin/grep", "\"user\":52")
cmd.Stdin = r
}
log.Print("FdwBegin ctx=", state)
}
//export FdwIterate
func FdwIterate(node *C.ForeignScanState) *C.TupleTableSlot {
state := cRetained(node.fdw_state).(*ExecState)
slot := node.ss.ss_ScanTupleSlot
C.ExecClearTuple(slot)
data, err := state.out.ReadBytes('\n')
if err != nil {
if err != io.EOF {
log.Print(err)
}
return slot
}
data = data[0 : len(data)-1]
// log.Print("line: ", string(data))
tupDesc := slot.tts_tupleDescriptor // type C.TupDesc
n := int(tupDesc.natts)
// 1024 should be enough for anyone
if n > 1024 {
n = 1024
}
values := (*[1024]C.Datum)(unsafe.Pointer(slot.tts_values))
nulls := (*[1024]C.bool)(unsafe.Pointer(slot.tts_isnull))
descs := (*[1024]C.Form_pg_attribute)(unsafe.Pointer(tupDesc.attrs))
var decoded map[string]interface{}
var decoder *json.Decoder
for i := 0; i < n; i++ {
col := C.GoString(&descs[i].attname.data[0])
var value string
if col == "data" {
value = string(data)
} else if col == "file" {
value = "todo"
} else {
if decoder == nil {
decoder = json.NewDecoder(bytes.NewBuffer(data))
decoder.UseNumber()
err := decoder.Decode(&decoded)
if err != nil {
log.Print(err)
return slot
}
}
v, ok := decoded[col]
if !ok {
nulls[i] = C.true
continue
}
switch vv := v.(type) {
case string:
value = vv
case json.Number:
value = vv.String()
case bool:
if vv {
value = "T"
} else {
value = "F"
}
}
}
typ := descs[i].atttypid // C.Oid
mod := descs[i].atttypmod // C.uint32
values[i] = makeDatum(value, typ, mod)
if values[i] == (C.Datum)(0) {
nulls[i] = C.true
} else {
nulls[i] = C.false
}
}
state.count++
C.ExecStoreVirtualTuple(slot)
return slot
}
//export FdwReScan
func FdwReScan(node *C.ForeignScanState) {
log.Print("FdwReScan")
}
//export FdwEnd
func FdwEnd(node *C.ForeignScanState) {
state := cRetained(node.fdw_state).(*ExecState)
log.Print("FdwEnd ctx=", state)
for _, cmd := range state.cmds {
log.Print(" kill ", cmd.Process.Pid)
cmd.Process.Kill()
cmd.Wait()
}
node.fdw_state = nil
cRelease(state)
}
func getNodeTag(ptr unsafe.Pointer) C.NodeTag {
return ((*C.Node)(ptr))._type
}
// golang somehow types C.PgFunction as *[0]byte
type pgFunc *[0]byte
func makeDatum(data string, typ C.Oid, mod C.int32) C.Datum {
cData := C.CString(data)
defer C.free(unsafe.Pointer(cData))
datum := (C.Datum)(uintptr(unsafe.Pointer(cData)))
// this is now a c-string (0-terminated) pg Datum
switch typ {
case 16: // BOOLID
return C.DirectFunctionCall1Coll((pgFunc)(C.boolin), C.InvalidOid, datum)
case 21: // INT2OID
return C.DirectFunctionCall1Coll((pgFunc)(C.int2in), C.InvalidOid, datum)
case 23: // INT4OID
return C.DirectFunctionCall1Coll((pgFunc)(C.int4in), C.InvalidOid, datum)
case 25: // TEXTOID
// alternative: convert via C.cstring_to_text(C.CString(data))
return C.DirectFunctionCall1Coll((pgFunc)(C.textin), C.InvalidOid, datum)
default:
return C.Datum(0)
}
}
// iterates a *C.List
func iterateList(list *C.List, cb func(unsafe.Pointer)) {
if list == nil {
return
}
for cell := list.head; cell != nil; cell = cell.next {
// &cell.data[0] is the address of the (data in) cell, dereference to get the value
cb(*(*unsafe.Pointer)(unsafe.Pointer(&cell.data[0])))
}
}
func getDir(tableId C.Oid) string {
var ret string
cb := func(ptr unsafe.Pointer) {
elem := (*C.DefElem)(ptr)
name := C.GoString(elem.defname)
value := C.GoString(C.defGetString(elem))
if name == "directory" {
ret = value
}
}
table := C.GetForeignTable(tableId)
iterateList(C.GetForeignServer(table.serverid).options, cb)
iterateList(table.options, cb)
return ret
}
// retain stuff for gc so we can pass it through C
var cMap = make(map[uintptr]interface{})
// should be passed a pointer!
func cRetain(x interface{}) unsafe.Pointer {
ptr := reflect.ValueOf(x).Pointer()
cMap[ptr] = x
return unsafe.Pointer(ptr)
}
func cRetained(ptr unsafe.Pointer) interface{} {
return cMap[uintptr(ptr)]
}
func cRelease(x interface{}) {
ptr := reflect.ValueOf(x).Pointer()
delete(cMap, ptr)
}
func main() {}