super-graph/psql/tables.go

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package psql
import (
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"context"
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"fmt"
"strings"
"github.com/gobuffalo/flect"
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"github.com/jackc/pgx/pgtype"
"github.com/jackc/pgx/v4/pgxpool"
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)
type DBTable struct {
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Name string
Type string
}
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func GetTables(dbc *pgxpool.Conn) ([]*DBTable, error) {
sqlStmt := `
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SELECT
c.relname as "name",
CASE c.relkind WHEN 'r' THEN 'table'
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WHEN 'v' THEN 'view'
WHEN 'm' THEN 'materialized view'
WHEN 'f' THEN 'foreign table'
END as "type"
FROM pg_catalog.pg_class c
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LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
WHERE c.relkind IN ('r','v','m','f','')
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AND n.nspname <> 'pg_catalog'
AND n.nspname <> 'information_schema'
AND n.nspname !~ '^pg_toast'
AND pg_catalog.pg_table_is_visible(c.oid);`
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var tables []*DBTable
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rows, err := dbc.Query(context.Background(), sqlStmt)
if err != nil {
return nil, fmt.Errorf("Error fetching tables: %s", err)
}
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defer rows.Close()
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for rows.Next() {
t := DBTable{}
err = rows.Scan(&t.Name, &t.Type)
if err != nil {
return nil, err
}
tables = append(tables, &t)
}
return tables, nil
}
type DBColumn struct {
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ID int
Name string
Type string
NotNull bool
PrimaryKey bool
UniqueKey bool
FKeyTable string
FKeyColID []int
fKeyColID pgtype.Int2Array
}
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func GetColumns(dbc *pgxpool.Conn, schema, table string) ([]*DBColumn, error) {
sqlStmt := `
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SELECT
f.attnum AS id,
f.attname AS name,
f.attnotnull AS notnull,
pg_catalog.format_type(f.atttypid,f.atttypmod) AS type,
CASE
WHEN p.contype = ('p'::char) THEN true
ELSE false
END AS primarykey,
CASE
WHEN p.contype = ('u'::char) THEN true
ELSE false
END AS uniquekey,
CASE
WHEN p.contype = ('f'::char) THEN g.relname
ELSE ''::text
END AS foreignkey,
CASE
WHEN p.contype = ('f'::char) THEN p.confkey
ELSE ARRAY[]::int2[]
END AS foreignkey_fieldnum
FROM pg_attribute f
JOIN pg_class c ON c.oid = f.attrelid
LEFT JOIN pg_attrdef d ON d.adrelid = c.oid AND d.adnum = f.attnum
LEFT JOIN pg_namespace n ON n.oid = c.relnamespace
LEFT JOIN pg_constraint p ON p.conrelid = c.oid AND f.attnum = ANY (p.conkey)
LEFT JOIN pg_class AS g ON p.confrelid = g.oid
WHERE c.relkind = ('r'::char)
AND n.nspname = $1 -- Replace with Schema name
AND c.relname = $2 -- Replace with table name
AND f.attnum > 0
AND f.attisdropped = false
ORDER BY id;`
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rows, err := dbc.Query(context.Background(), sqlStmt, schema, table)
if err != nil {
return nil, fmt.Errorf("error fetching columns: %s", err)
}
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defer rows.Close()
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cmap := make(map[int]*DBColumn)
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for rows.Next() {
c := DBColumn{}
err = rows.Scan(&c.ID, &c.Name, &c.NotNull, &c.Type, &c.PrimaryKey, &c.UniqueKey,
&c.FKeyTable, &c.fKeyColID)
if err != nil {
return nil, err
}
c.fKeyColID.AssignTo(&c.FKeyColID)
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if v, ok := cmap[c.ID]; ok {
if c.PrimaryKey {
v.PrimaryKey = true
}
if c.NotNull {
v.NotNull = true
}
if c.UniqueKey {
v.UniqueKey = true
}
} else {
cmap[c.ID] = &c
}
}
cols := make([]*DBColumn, 0, len(cmap))
for _, v := range cmap {
cols = append(cols, v)
}
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return cols, nil
}
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type DBSchema struct {
t map[string]*DBTableInfo
rm map[string]map[string]*DBRel
al map[string]struct{}
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}
type DBTableInfo struct {
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Name string
Singular bool
PrimaryCol string
TSVCol string
Columns map[string]*DBColumn
ColumnNames []string
}
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type RelType int
const (
RelBelongTo RelType = iota + 1
RelOneToMany
RelOneToManyThrough
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RelRemote
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)
type DBRel struct {
Type RelType
Through string
ColT string
Col1 string
Col2 string
}
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func NewDBSchema(db *pgxpool.Pool, aliases map[string][]string) (*DBSchema, error) {
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schema := &DBSchema{
t: make(map[string]*DBTableInfo),
rm: make(map[string]map[string]*DBRel),
al: make(map[string]struct{}),
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}
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dbc, err := db.Acquire(context.Background())
if err != nil {
return nil, fmt.Errorf("error acquiring connection from pool")
}
defer dbc.Release()
tables, err := GetTables(dbc)
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if err != nil {
return nil, err
}
for _, t := range tables {
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cols, err := GetColumns(dbc, "public", t.Name)
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if err != nil {
return nil, err
}
schema.updateSchema(t, cols, aliases)
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}
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return schema, nil
}
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func (s *DBSchema) updateSchema(
t *DBTable,
cols []*DBColumn,
aliases map[string][]string) {
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// Foreign key columns in current table
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colByID := make(map[int]*DBColumn)
columns := make(map[string]*DBColumn, len(cols))
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colNames := make([]string, 0, len(cols))
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for i := range cols {
c := cols[i]
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name := strings.ToLower(c.Name)
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columns[name] = c
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colNames = append(colNames, name)
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colByID[c.ID] = c
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}
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singular := strings.ToLower(flect.Singularize(t.Name))
s.t[singular] = &DBTableInfo{
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Name: t.Name,
Singular: true,
Columns: columns,
ColumnNames: colNames,
}
plural := strings.ToLower(flect.Pluralize(t.Name))
s.t[plural] = &DBTableInfo{
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Name: t.Name,
Singular: false,
Columns: columns,
ColumnNames: colNames,
}
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ct := strings.ToLower(t.Name)
if al, ok := aliases[ct]; ok {
for i := range al {
k1 := flect.Singularize(al[i])
s.t[k1] = s.t[singular]
k2 := flect.Pluralize(al[i])
s.t[k2] = s.t[plural]
s.al[k1] = struct{}{}
s.al[k2] = struct{}{}
}
}
jcols := make([]*DBColumn, 0, len(cols))
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for _, c := range cols {
switch {
case c.Type == "tsvector":
s.t[singular].TSVCol = c.Name
s.t[plural].TSVCol = c.Name
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case c.PrimaryKey:
s.t[singular].PrimaryCol = c.Name
s.t[plural].PrimaryCol = c.Name
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case len(c.FKeyTable) != 0:
if len(c.FKeyColID) == 0 {
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continue
}
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// Foreign key column name
ft := strings.ToLower(c.FKeyTable)
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fc, ok := colByID[c.FKeyColID[0]]
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if !ok {
continue
}
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// Belongs-to relation between current table and the
// table in the foreign key
rel1 := &DBRel{RelBelongTo, "", "", c.Name, fc.Name}
s.SetRel(ct, ft, rel1)
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// One-to-many relation between the foreign key table and the
// the current table
rel2 := &DBRel{RelOneToMany, "", "", fc.Name, c.Name}
s.SetRel(ft, ct, rel2)
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jcols = append(jcols, c)
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}
}
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// If table contains multiple foreign key columns it's a possible
// join table for many-to-many relationships or multiple one-to-many
// relations
// Below one-to-many relations use the current table as the
// join table aka through table.
if len(jcols) > 1 {
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for i := range jcols {
for n := range jcols {
if n != i {
s.updateSchemaOTMT(ct, jcols[i], jcols[n], colByID)
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}
}
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}
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}
}
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func (s *DBSchema) updateSchemaOTMT(
ct string,
col1, col2 *DBColumn,
colByID map[int]*DBColumn) {
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t1 := strings.ToLower(col1.FKeyTable)
t2 := strings.ToLower(col2.FKeyTable)
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fc1, ok := colByID[col1.FKeyColID[0]]
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if !ok {
return
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}
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fc2, ok := colByID[col2.FKeyColID[0]]
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if !ok {
return
}
// One-to-many-through relation between 1nd foreign key table and the
// 2nd foreign key table
//rel1 := &DBRel{RelOneToManyThrough, ct, fc1.Name, col1.Name}
rel1 := &DBRel{RelOneToManyThrough, ct, col2.Name, fc2.Name, col1.Name}
s.SetRel(t1, t2, rel1)
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// One-to-many-through relation between 2nd foreign key table and the
// 1nd foreign key table
//rel2 := &DBRel{RelOneToManyThrough, ct, col2.Name, fc2.Name}
rel2 := &DBRel{RelOneToManyThrough, ct, col1.Name, fc1.Name, col2.Name}
s.SetRel(t2, t1, rel2)
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}
func (s *DBSchema) GetTable(table string) (*DBTableInfo, error) {
t, ok := s.t[table]
if !ok {
return nil, fmt.Errorf("unknown table '%s'", table)
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}
return t, nil
}
func (s *DBSchema) SetRel(child, parent string, rel *DBRel) error {
sc := strings.ToLower(flect.Singularize(child))
pc := strings.ToLower(flect.Pluralize(child))
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if _, ok := s.rm[sc]; !ok {
s.rm[sc] = make(map[string]*DBRel)
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}
if _, ok := s.rm[pc]; !ok {
s.rm[pc] = make(map[string]*DBRel)
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}
sp := strings.ToLower(flect.Singularize(parent))
pp := strings.ToLower(flect.Pluralize(parent))
s.rm[sc][sp] = rel
s.rm[sc][pp] = rel
s.rm[pc][sp] = rel
s.rm[pc][pp] = rel
return nil
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}
func (s *DBSchema) GetRel(child, parent string) (*DBRel, error) {
rel, ok := s.rm[child][parent]
if !ok {
return nil, fmt.Errorf("unknown relationship '%s' -> '%s'",
child, parent)
}
return rel, nil
}
func (s *DBSchema) IsAlias(name string) bool {
_, ok := s.al[name]
return ok
}