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alter.go
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alter.go
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package postgres
import (
"fmt"
"strings"
"github.com/lib/pq"
schemasv1alpha3 "github.com/schemahero/schemahero/pkg/apis/schemas/v1alpha3"
"github.com/schemahero/schemahero/pkg/database/types"
)
func AlterColumnStatements(tableName string, primaryKeys []string, desiredColumns []*schemasv1alpha3.SQLTableColumn, existingColumn *types.Column) ([]string, error) {
alterStatement := fmt.Sprintf("alter column %s", pq.QuoteIdentifier(existingColumn.Name))
// this could be an alter or a drop column command
for _, desiredColumn := range desiredColumns {
if desiredColumn.Name == existingColumn.Name {
column, err := schemaColumnToColumn(desiredColumn)
if err != nil {
return nil, err
}
if columnsMatch(existingColumn, column) {
return []string{}, nil
}
// If the request is to modify a column to add a not null contraint to an existing column
// handle that part here
if column.Constraints != nil && column.Constraints.NotNull != nil && *column.Constraints.NotNull == true {
isAddingNotNull := false
if existingColumn.Constraints == nil {
isAddingNotNull = true
} else if existingColumn.Constraints.NotNull == nil {
isAddingNotNull = true
} else if *existingColumn.Constraints.NotNull == false {
isAddingNotNull = true
}
if isAddingNotNull {
// the best plan here is:
// 1. add default
// 2. update values with default
// 3. set not null
statements := []string{}
// add default
if column.ColumnDefault != nil {
if existingColumn.ColumnDefault == nil || *existingColumn.ColumnDefault != *column.ColumnDefault {
localStatement := fmt.Sprintf("alter table %s alter column %s set default '%s'",
pq.QuoteIdentifier(tableName),
pq.QuoteIdentifier(existingColumn.Name),
*column.ColumnDefault)
statements = append(statements, localStatement)
}
}
// update existing values
if column.ColumnDefault != nil {
localStatement := fmt.Sprintf("update %s set %s='%s' where %s is null",
pq.QuoteIdentifier(tableName),
pq.QuoteIdentifier(existingColumn.Name),
*column.ColumnDefault,
pq.QuoteIdentifier(existingColumn.Name))
statements = append(statements, localStatement)
}
// set not null
localStatement := fmt.Sprintf("alter table %s alter column %s set not null",
pq.QuoteIdentifier(tableName),
pq.QuoteIdentifier(existingColumn.Name))
statements = append(statements, localStatement)
return statements, nil
}
}
changes := []string{}
if existingColumn.DataType != column.DataType {
changes = append(changes, fmt.Sprintf("%s type %s", alterStatement, column.DataType))
} else if column.DataType == existingColumn.DataType {
if column.IsArray != existingColumn.IsArray {
changes = append(changes, fmt.Sprintf("%s type %s[] using %s::%s[]", alterStatement, column.DataType, pq.QuoteIdentifier(existingColumn.Name), column.DataType))
}
}
if column.ColumnDefault != nil {
if existingColumn.ColumnDefault == nil || *column.ColumnDefault != *existingColumn.ColumnDefault {
changes = append(changes, fmt.Sprintf("%s set default '%s'", alterStatement, *column.ColumnDefault))
}
} else if existingColumn.ColumnDefault != nil {
changes = append(changes, fmt.Sprintf("%s drop default", alterStatement))
}
// too much complexity below!
if column.Constraints != nil || existingColumn.Constraints != nil {
isPrimaryKey := false
for _, primaryKey := range primaryKeys {
if column.Name == primaryKey {
isPrimaryKey = true
}
}
if !isPrimaryKey {
if existingColumn.Constraints != nil && existingColumn.Constraints.NotNull != nil && *existingColumn.Constraints.NotNull == true {
if column.Constraints == nil || column.Constraints.NotNull == nil || *column.Constraints.NotNull == false {
changes = append(changes, fmt.Sprintf("%s drop not null", alterStatement))
}
}
}
}
if len(changes) == 0 {
// no changes
return []string{}, nil
}
return []string{fmt.Sprintf(`alter table %s %s`, pq.QuoteIdentifier(tableName), strings.Join(changes, ", "))}, nil
}
}
return []string{fmt.Sprintf(`alter table %s drop column %s`, pq.QuoteIdentifier(tableName), pq.QuoteIdentifier(existingColumn.Name))}, nil
}
func columnsMatch(col1 *types.Column, col2 *types.Column) bool {
if col1.DataType != col2.DataType {
return false
}
if col1.IsArray != col2.IsArray {
return false
}
if col1.ColumnDefault != nil && col2.ColumnDefault == nil {
return false
} else if col1.ColumnDefault == nil && col2.ColumnDefault != nil {
return false
} else if col1.ColumnDefault != nil && col2.ColumnDefault != nil && *col1.ColumnDefault != *col2.ColumnDefault {
return false
}
col1Constraints, col2Constraints := col1.Constraints, col2.Constraints
if col1Constraints == nil {
col1Constraints = &types.ColumnConstraints{}
}
if col2Constraints == nil {
col2Constraints = &types.ColumnConstraints{}
}
return types.NotNullConstraintEquals(col1Constraints.NotNull, col2Constraints.NotNull)
}