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Support partitioned table CDC #581

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merged 3 commits into from
Oct 26, 2023
Merged

Support partitioned table CDC #581

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01eb700
Support partitioned table CDC for older PG versions
iskakaushik Oct 26, 2023
5a5e211
simple query protocol
iskakaushik Oct 26, 2023
2d30e5f
fix typo
iskakaushik Oct 26, 2023
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84 changes: 72 additions & 12 deletions flow/connectors/postgres/cdc.go
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@ import (
"github.com/PeerDB-io/peer-flow/model"
"github.com/PeerDB-io/peer-flow/model/qvalue"
"github.com/jackc/pglogrepl"
"github.com/jackc/pgx/v5"
"github.com/jackc/pgx/v5/pgconn"
"github.com/jackc/pgx/v5/pgproto3"
"github.com/jackc/pgx/v5/pgtype"
Expand All @@ -32,6 +33,9 @@ type PostgresCDCSource struct {
startLSN pglogrepl.LSN
commitLock bool
customTypeMapping map[uint32]string

// for partitioned tables, maps child relid to parent relid
chIdToParRelId map[uint32]uint32
}

type PostgresCDCConfig struct {
Expand All @@ -46,6 +50,11 @@ type PostgresCDCConfig struct {

// Create a new PostgresCDCSource
func NewPostgresCDCSource(cdcConfig *PostgresCDCConfig, customTypeMap map[uint32]string) (*PostgresCDCSource, error) {
childToParentRelIdMap, err := getChildToParentRelIdMap(cdcConfig.AppContext, cdcConfig.Connection)
if err != nil {
return nil, fmt.Errorf("error getting child to parent relid map: %w", err)
}

return &PostgresCDCSource{
ctx: cdcConfig.AppContext,
replPool: cdcConfig.Connection,
Expand All @@ -55,11 +64,44 @@ func NewPostgresCDCSource(cdcConfig *PostgresCDCConfig, customTypeMap map[uint32
publication: cdcConfig.Publication,
relationMessageMapping: cdcConfig.RelationMessageMapping,
typeMap: pgtype.NewMap(),
chIdToParRelId: childToParentRelIdMap,
commitLock: false,
customTypeMapping: customTypeMap,
}, nil
}

func getChildToParentRelIdMap(ctx context.Context, pool *pgxpool.Pool) (map[uint32]uint32, error) {
query := `
SELECT
parent.oid AS parentrelid,
child.oid AS childrelid
FROM pg_inherits
JOIN pg_class parent ON pg_inherits.inhparent = parent.oid
JOIN pg_class child ON pg_inherits.inhrelid = child.oid
WHERE parent.relkind='p';
`

rows, err := pool.Query(ctx, query, pgx.QueryExecModeSimpleProtocol)
if err != nil {
return nil, fmt.Errorf("error querying for child to parent relid map: %w", err)
}

defer rows.Close()

childToParentRelIdMap := make(map[uint32]uint32)
for rows.Next() {
var parentRelId uint32
var childRelId uint32
err := rows.Scan(&parentRelId, &childRelId)
if err != nil {
return nil, fmt.Errorf("error scanning child to parent relid map: %w", err)
}
childToParentRelIdMap[childRelId] = parentRelId
}

return childToParentRelIdMap, nil
}

// PullRecords pulls records from the cdc stream
func (p *PostgresCDCSource) PullRecords(req *model.PullRecordsRequest) (
*model.RecordsWithTableSchemaDelta, error) {
Expand Down Expand Up @@ -348,6 +390,9 @@ func (p *PostgresCDCSource) processMessage(batch *model.RecordBatch, xld pglogre
batch.LastCheckPointID = int64(xld.WALStart)
p.commitLock = false
case *pglogrepl.RelationMessage:
// treat all relation messages as correponding to parent if partitioned.
msg.RelationID = p.getParentRelIdIfPartitioned(msg.RelationID)

// TODO (kaushik): consider persistent state for a mirror job
// to be stored somewhere in temporal state. We might need to persist
// the state of the relation message somewhere
Expand All @@ -373,17 +418,19 @@ func (p *PostgresCDCSource) processInsertMessage(
lsn pglogrepl.LSN,
msg *pglogrepl.InsertMessage,
) (model.Record, error) {
tableName, exists := p.SrcTableIDNameMapping[msg.RelationID]
relId := p.getParentRelIdIfPartitioned(msg.RelationID)

tableName, exists := p.SrcTableIDNameMapping[relId]
if !exists {
return nil, nil
}

// log lsn and relation id for debugging
log.Debugf("InsertMessage => LSN: %d, RelationID: %d, Relation Name: %s", lsn, msg.RelationID, tableName)
log.Debugf("InsertMessage => LSN: %d, RelationID: %d, Relation Name: %s", lsn, relId, tableName)

rel, ok := p.relationMessageMapping[msg.RelationID]
rel, ok := p.relationMessageMapping[relId]
if !ok {
return nil, fmt.Errorf("unknown relation id: %d", msg.RelationID)
return nil, fmt.Errorf("unknown relation id: %d", relId)
}

// create empty map of string to interface{}
Expand All @@ -405,17 +452,19 @@ func (p *PostgresCDCSource) processUpdateMessage(
lsn pglogrepl.LSN,
msg *pglogrepl.UpdateMessage,
) (model.Record, error) {
tableName, exists := p.SrcTableIDNameMapping[msg.RelationID]
relID := p.getParentRelIdIfPartitioned(msg.RelationID)

tableName, exists := p.SrcTableIDNameMapping[relID]
if !exists {
return nil, nil
}

// log lsn and relation id for debugging
log.Debugf("UpdateMessage => LSN: %d, RelationID: %d, Relation Name: %s", lsn, msg.RelationID, tableName)
log.Debugf("UpdateMessage => LSN: %d, RelationID: %d, Relation Name: %s", lsn, relID, tableName)

rel, ok := p.relationMessageMapping[msg.RelationID]
rel, ok := p.relationMessageMapping[relID]
if !ok {
return nil, fmt.Errorf("unknown relation id: %d", msg.RelationID)
return nil, fmt.Errorf("unknown relation id: %d", relID)
}

// create empty map of string to interface{}
Expand Down Expand Up @@ -444,17 +493,19 @@ func (p *PostgresCDCSource) processDeleteMessage(
lsn pglogrepl.LSN,
msg *pglogrepl.DeleteMessage,
) (model.Record, error) {
tableName, exists := p.SrcTableIDNameMapping[msg.RelationID]
relID := p.getParentRelIdIfPartitioned(msg.RelationID)

tableName, exists := p.SrcTableIDNameMapping[relID]
if !exists {
return nil, nil
}

// log lsn and relation id for debugging
log.Debugf("DeleteMessage => LSN: %d, RelationID: %d, Relation Name: %s", lsn, msg.RelationID, tableName)
log.Debugf("DeleteMessage => LSN: %d, RelationID: %d, Relation Name: %s", lsn, relID, tableName)

rel, ok := p.relationMessageMapping[msg.RelationID]
rel, ok := p.relationMessageMapping[relID]
if !ok {
return nil, fmt.Errorf("unknown relation id: %d", msg.RelationID)
return nil, fmt.Errorf("unknown relation id: %d", relID)
}

// create empty map of string to interface{}
Expand Down Expand Up @@ -668,3 +719,12 @@ func (p *PostgresCDCSource) compositePKeyToString(req *model.PullRecordsRequest,
hasher.Write(pkeyColsMerged)
return fmt.Sprintf("%x", hasher.Sum(nil)), nil
}

func (p *PostgresCDCSource) getParentRelIdIfPartitioned(relId uint32) uint32 {
parentRelId, ok := p.chIdToParRelId[relId]
if ok {
return parentRelId
}

return relId
}
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