support PG 9.4

Author: vynaloze

.travis.yml

@@ -17,6 +17,7 @@ env:
   - PG_VERSION=10
   - PG_VERSION=9.6
   - PG_VERSION=9.5
+  - PG_VERSION=9.4
 
 before_install:
   - sudo /etc/init.d/postgresql stop

README.md

@@ -89,6 +89,7 @@ conn, err := pgstats.Connect("foo", "username", "password", pgstats.SslMode("dis
 - 10
 - 9.6
 - 9.5
+- 9.4
 
 [Full pg_stat view / version table](https://github.com/vynaloze/pgstats/wiki/Supported-stats-vs-PG-version)
 
@@ -101,7 +102,7 @@ Y | `v0.2.0` | pg_stat_statements | ~June '19
 Y | `v0.3.0` | support PG 11 | ~June '19
 Y | `v0.4.0` | support PG 9.6 | ~June '19
 Y | `v0.5.0` | support PG 9.5 | ~June '19
-N | `v0.6.0` | support PG 9.4 | ~June '19
+Y | `v0.6.0` | support PG 9.4 | ~June '19
 N | `v1.0.0` | global wrapper for the ease of use | ~July '19
 N | `v1.1.0` | add missing integration tests | ~July '19
 

pgstats.go

@@ -70,6 +70,8 @@ func (s *PgStats) PgStatSubscription() (PgStatSubscriptionView, error) {
 // PgStatSsl returns a slice, containing statistics about SSL usage
 // on the connection for each backend or WAL sender process.
 //
+// Supported since PostgreSQL 9.5.
+//
 // For more details, see:
 // https://www.postgresql.org/docs/current/monitoring-stats.html#PG-STAT-SSL
 func (s *PgStats) PgStatSsl() (PgStatSslView, error) {

pgstats_integration_test.go

@@ -63,7 +63,15 @@ func TestPgSsl(t *testing.T) {
 		t.Error(err)
 	}
 	a, err := s.PgStatSsl()
-	validate(t, len(a), err)
+	if err != nil {
+		if strings.Contains(err.Error(), "Unsupported PostgreSQL version: 9.") {
+			return
+		}
+		t.Error(err)
+	}
+	if len(a) == 0 {
+		t.Error("No data returned by query")
+	}
 }
 
 func TestPgStatProgressVacuum(t *testing.T) {

stat_ssl.go

@@ -1,6 +1,9 @@
 package pgstats
 
-import "database/sql"
+import (
+	"database/sql"
+	"github.com/pkg/errors"
+)
 
 // PgStatSslView represents content of pg_stat_ssl view
 type PgStatSslView []PgStatSslRow
@@ -26,6 +29,14 @@ type PgStatSslRow struct {
 }
 
 func (s *PgStats) fetchSsl() (PgStatSslView, error) {
+	version, err := s.getPgVersion()
+	if err != nil {
+		return nil, err
+	}
+	if version < 9.5 {
+		return nil, errors.Errorf("Unsupported PostgreSQL version: %f", version)
+	}
+
 	db := s.conn.db
 	query := "select pid,ssl,version,cipher,bits," +
 		"compression,clientdn from pg_stat_ssl"

stat_statements.go

@@ -16,14 +16,19 @@ type PgStatStatementsRow struct {
 	// Number of times executed
 	Calls int64 `json:"calls"`
 	// Total time spent in the statement, in milliseconds
+	// Supported since PostgreSQL 9.5
 	TotalTime float64 `json:"total_time"`
 	// Minimum time spent in the statement, in milliseconds
+	// Supported since PostgreSQL 9.5
 	MinTime float64 `json:"min_time"`
 	// Maximum time spent in the statement, in milliseconds
+	// Supported since PostgreSQL 9.5
 	MaxTime float64 `json:"max_time"`
 	// Mean time spent in the statement, in milliseconds
+	// Supported since PostgreSQL 9.5
 	MeanTime float64 `json:"mean_time"`
 	// Population standard deviation of time spent in the statement, in milliseconds
+	// Supported since PostgreSQL 9.5
 	StddevTime float64 `json:"stddev_time"`
 	// Total number of rows retrieved or affected by the statement
 	Rows int64 `json:"rows"`
@@ -54,6 +59,17 @@ type PgStatStatementsRow struct {
 }
 
 func (s *PgStats) fetchStatements() (PgStatStatementsView, error) {
+	version, err := s.getPgVersion()
+	if err != nil {
+		return nil, err
+	}
+	if version > 9.4 {
+		return s.fetchStatements95()
+	}
+	return s.fetchStatements94()
+}
+
+func (s *PgStats) fetchStatements95() (PgStatStatementsView, error) {
 	db := s.conn.db
 	query := "select userid,dbid,queryid,query,calls," +
 		"total_time,min_time,max_time,mean_time,stddev_time," +
@@ -82,3 +98,31 @@ func (s *PgStats) fetchStatements() (PgStatStatementsView, error) {
 	}
 	return data, rows.Err()
 }
+
+func (s *PgStats) fetchStatements94() (PgStatStatementsView, error) {
+	db := s.conn.db
+	query := "select userid,dbid,queryid,query,calls," +
+		"rows,shared_blks_hit,shared_blks_read,shared_blks_dirtied,shared_blks_written," +
+		"local_blks_hit,local_blks_read,local_blks_dirtied,local_blks_written,temp_blks_read," +
+		"temp_blks_written,blk_read_time,blk_write_time from pg_stat_statements"
+
+	rows, err := db.Query(query)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	data := make([]PgStatStatementsRow, 0)
+	for rows.Next() {
+		row := new(PgStatStatementsRow)
+		err := rows.Scan(&row.Userid, &row.Dbid, &row.Queryid, &row.Query, &row.Calls,
+			&row.Rows, &row.SharedBlksHit, &row.SharedBlksRead, &row.SharedBlksDirtied, &row.SharedBlksWritten,
+			&row.LocalBlksHit, &row.LocalBlksRead, &row.LocalBlksDirtied, &row.LocalBlksWritten, &row.TempBlksRead,
+			&row.TempBlksWritten, &row.BlkReadTime, &row.BlkWriteTime)
+		if err != nil {
+			return nil, err
+		}
+		data = append(data, *row)
+	}
+	return data, rows.Err()
+}