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PostgreSQL: heap tuples implementation
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Pavel Safonov committed Jul 29, 2022
1 parent 51878dc commit ce9ae76
Showing 1 changed file with 169 additions and 7 deletions.
176 changes: 169 additions & 7 deletions format/postgres/flavours/postgres14/pgheap.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ import (
"context"
"github.com/wader/fq/format/postgres/common"
"github.com/wader/fq/pkg/decode"
"github.com/wader/fq/pkg/scalar"
)

// type = struct PageHeaderData
Expand Down Expand Up @@ -35,6 +36,47 @@ import (
// typedef uint16 LocationIndex;
// #define SizeOfPageHeaderData (offsetof(PageHeaderData, pd_linp))

// type = struct HeapTupleHeaderData {
/* 0 | 12 */ // union {
/* 12 */ // HeapTupleFields t_heap;
/* 12 */ // DatumTupleFields t_datum;
//
/* total size (bytes): 12 */
/* } t_choice; //
/* 12 | 6 */ // ItemPointerData t_ctid;
/* 18 | 2 */ // uint16 t_infomask2;
/* 20 | 2 */ // uint16 t_infomask;
/* 22 | 1 */ // uint8 t_hoff;
/* 23 | 0 */ // bits8 t_bits[];
/* XXX 1-byte padding */
//
/* total size (bytes): 24 */
const SizeOfHeapTupleHeaderData = 24

// type = struct HeapTupleFields {
/* 0 | 4 */ // TransactionId t_xmin;
/* 4 | 4 */ // TransactionId t_xmax;
/* 8 | 4 */ // union {
/* 4 */ // CommandId t_cid;
/* 4 */ // TransactionId t_xvac;
// } t_field3;
/* total size (bytes): 4 */
//
/* total size (bytes): 12 */

// type = struct DatumTupleFields {
/* 0 | 4 */ // int32 datum_len_;
/* 4 | 4 */ // int32 datum_typmod;
/* 8 | 4 */ // Oid datum_typeid;
//
/* total size (bytes): 12 */

// type = struct ItemPointerData {
/* 0 | 4 */ // BlockIdData ip_blkid;
/* 4 | 2 */ // OffsetNumber ip_posid;
//
/* total size (bytes): 6 */

type heapD struct {
pageSize uint64

Expand All @@ -47,6 +89,26 @@ type heapPageD struct {
pdUpper uint16
pdSpecial uint16
pd_pagesize_version uint16

itemIds []itemIdDataD
}

func (hp *heapPageD) getItemId(offset uint32) (bool, itemIdDataD) {
for _, id := range hp.itemIds {
if id.lpOff == offset {
return true, id
}
}
return false, itemIdDataD{}
}

type itemIdDataD struct {
/* 0: 0 | 4 */ // unsigned int lp_off: 15
/* 1: 7 | 4 */ // unsigned int lp_flags: 2
/* 2: 1 | 4 */ // unsigned int lp_len: 15
lpOff uint32
lpFlags uint32
lpLen uint32
}

func getHeapD(d *decode.D) *heapD {
Expand All @@ -70,12 +132,13 @@ func DecodeHeap(d *decode.D) any {

func decodeHeapPages(d *decode.D) {
heap := getHeapD(d)
page := &heapPageD{}
heap.page = page

pagePosBegin := common.RoundDown(heap.pageSize, uint64(d.Pos()/8))

for {
page := &heapPageD{}
heap.page = page

pagePosBegin := common.RoundDown(heap.pageSize, uint64(d.Pos()/8))

d.FieldStruct("HeapPage", func(d *decode.D) {
/* 0 | 8 */ // PageXLogRecPtr pd_lsn;
/* 8 | 2 */ // uint16 pd_checksum;
Expand Down Expand Up @@ -113,18 +176,117 @@ func decodeHeapPages(d *decode.D) {
/* 1: 7 | 4 */ // unsigned int lp_flags: 2
/* 2: 1 | 4 */ // unsigned int lp_len: 15
d.FieldStruct("ItemIdData", func(d *decode.D) {
itemId := itemIdDataD{}

itemPos := d.Pos()
d.FieldU32("lp_off", common.LpOffMapper)
itemId.lpOff = uint32(d.FieldU32("lp_off", common.LpOffMapper))
d.SeekAbs(itemPos)
d.FieldU32("lp_flags", common.LpFlagsMapper)
itemId.lpFlags = uint32(d.FieldU32("lp_flags", common.LpFlagsMapper))
d.SeekAbs(itemPos)
d.FieldU32("lp_len", common.LpLenMapper)
itemId.lpLen = uint32(d.FieldU32("lp_len", common.LpLenMapper))

page.itemIds = append(page.itemIds, itemId)
})
} // for pd_linp
}) // pd_linp in PageHeaderData

}) // PageHeaderData, PageHeader

// free space
freeSpaceEnd := int64(pagePosBegin*8) + int64(page.pdUpper*8)
freeSpaceNBits := freeSpaceEnd - d.Pos()
d.FieldRawLen("FreeSpace", freeSpaceNBits, scalar.RawHex)

// Tuples
d.FieldArray("Tuples", func(d *decode.D) {
for i := 0; i < len(page.itemIds); i++ {
id := page.itemIds[i]
if id.lpOff == 0 || id.lpLen == 0 {
continue
}

pos := int64(pagePosBegin)*8 + int64(page.itemIds[i].lpOff)*8
tupleDataLen := id.lpLen - SizeOfHeapTupleHeaderData

d.SeekAbs(pos)

/* 0 | 12 */ // union {
/* 12 */ // HeapTupleFields t_heap;
/* 12 */ // DatumTupleFields t_datum;
// } t_choice;
/* total size (bytes): 12 */
/*
/* 12 | 6 */ // ItemPointerData t_ctid;
/* 18 | 2 */ // uint16 t_infomask2;
/* 20 | 2 */ // uint16 t_infomask;
/* 22 | 1 */ // uint8 t_hoff;
/* 23 | 0 */ // bits8 t_bits[];
/* XXX 1-byte padding */
//
/* total size (bytes): 24 */
d.FieldStruct("HeapTupleHeaderData", func(d *decode.D) {
d.FieldStruct("t_choice", func(d *decode.D) {
pos1 := d.Pos()
// type = struct HeapTupleFields {
/* 0 | 4 */ // TransactionId t_xmin;
/* 4 | 4 */ // TransactionId t_xmax;
/* 8 | 4 */ // union {
/* 4 */ // CommandId t_cid;
/* 4 */ // TransactionId t_xvac;
// } t_field3;
/* total size (bytes): 4 */
//
/* total size (bytes): 12 */
d.FieldStruct("t_heap", func(d *decode.D) {
d.FieldU32("t_xmin")
d.FieldU32("t_xmax")
d.FieldStruct("t_field3", func(d *decode.D) {
pos2 := d.Pos()
d.FieldU32("t_cid")
d.SeekAbs(pos2)
d.FieldU32("t_xvac")
}) // t_field3
}) // HeapTupleFields t_heap

d.SeekAbs(pos1)
// type = struct DatumTupleFields {
/* 0 | 4 */ // int32 datum_len_;
/* 4 | 4 */ // int32 datum_typmod;
/* 8 | 4 */ // Oid datum_typeid;
//
/* total size (bytes): 12 */

// t_datum
d.FieldStruct("t_datum", func(d *decode.D) {
d.FieldS32("datum_len_")
d.FieldS32("datum_typmod")
d.FieldU32("datum_typeid")
}) // DatumTupleFields t_datum
}) // t_choice

d.FieldStruct("t_ctid", func(d *decode.D) {
/* 0 | 4 */ // BlockIdData ip_blkid;
/* 4 | 2 */ // OffsetNumber ip_posid;
d.FieldU32("ip_blkid")
d.FieldU16("ip_posid")
}) // ItemPointerData t_ctid

/* 18 | 2 */ // uint16 t_infomask2;
/* 20 | 2 */ // uint16 t_infomask;
/* 22 | 1 */ // uint8 t_hoff;
/* 23 | 0 */ // bits8 t_bits[];
/* XXX 1-byte padding */
d.FieldU16("t_infomask2")
d.FieldU16("t_infomask")
d.FieldU8("t_hoff")
d.U8()

d.FieldRawLen("t_bits", int64(tupleDataLen*8), scalar.RawHex)

}) // HeapTupleHeaderData
}
}) // Tuples

// end of page
endLen := uint64(d.Pos() / 8)
pageEnd := common.TypeAlign(heap.pageSize, endLen)
Expand Down

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