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|
package engine
import (
"context"
"fmt"
"strings"
"github.com/seaweedfs/seaweedfs/weed/query/sqltypes"
)
// executeDescribeStatement handles DESCRIBE table commands
// Shows table schema in PostgreSQL-compatible format
func (e *SQLEngine) executeDescribeStatement(ctx context.Context, tableName string, database string) (*QueryResult, error) {
if database == "" {
database = e.catalog.GetCurrentDatabase()
if database == "" {
database = "default"
}
}
// Auto-discover and register topic if not already in catalog (same logic as SELECT)
if _, err := e.catalog.GetTableInfo(database, tableName); err != nil {
// Topic not in catalog, try to discover and register it
if regErr := e.discoverAndRegisterTopic(ctx, database, tableName); regErr != nil {
fmt.Printf("Warning: Failed to discover topic %s.%s: %v\n", database, tableName, regErr)
return &QueryResult{Error: fmt.Errorf("topic %s.%s not found and auto-discovery failed: %v", database, tableName, regErr)}, regErr
}
}
// Get flat schema and key columns from broker
flatSchema, keyColumns, _, err := e.catalog.brokerClient.GetTopicSchema(ctx, database, tableName)
if err != nil {
return &QueryResult{Error: err}, err
}
// System columns to include in DESCRIBE output
systemColumns := []struct {
Name string
Type string
Extra string
}{
{"_ts", "TIMESTAMP", "System column: Message timestamp"},
{"_key", "VARBINARY", "System column: Message key"},
{"_source", "VARCHAR(255)", "System column: Data source (parquet/log)"},
}
// If no schema is defined, include _value field
if flatSchema == nil {
systemColumns = append(systemColumns, struct {
Name string
Type string
Extra string
}{SW_COLUMN_NAME_VALUE, "VARBINARY", "Raw message value (no schema defined)"})
}
// Calculate total rows: schema fields + system columns
totalRows := len(systemColumns)
if flatSchema != nil {
totalRows += len(flatSchema.Fields)
}
// Create key column lookup map
keyColumnMap := make(map[string]bool)
for _, keyCol := range keyColumns {
keyColumnMap[keyCol] = true
}
result := &QueryResult{
Columns: []string{"Field", "Type", "Null", "Key", "Default", "Extra"},
Rows: make([][]sqltypes.Value, totalRows),
}
rowIndex := 0
// Add schema fields - mark key columns appropriately
if flatSchema != nil {
for _, field := range flatSchema.Fields {
sqlType := e.convertMQTypeToSQL(field.Type)
isKey := keyColumnMap[field.Name]
keyType := ""
if isKey {
keyType = "PRI" // Primary key
}
extra := "Data field"
if isKey {
extra = "Key field"
}
result.Rows[rowIndex] = []sqltypes.Value{
sqltypes.NewVarChar(field.Name),
sqltypes.NewVarChar(sqlType),
sqltypes.NewVarChar("YES"),
sqltypes.NewVarChar(keyType),
sqltypes.NewVarChar("NULL"),
sqltypes.NewVarChar(extra),
}
rowIndex++
}
}
// Add system columns
for _, sysCol := range systemColumns {
result.Rows[rowIndex] = []sqltypes.Value{
sqltypes.NewVarChar(sysCol.Name), // Field
sqltypes.NewVarChar(sysCol.Type), // Type
sqltypes.NewVarChar("YES"), // Null
sqltypes.NewVarChar("SYS"), // Key - mark as system column
sqltypes.NewVarChar("NULL"), // Default
sqltypes.NewVarChar(sysCol.Extra), // Extra - description
}
rowIndex++
}
return result, nil
}
// Enhanced executeShowStatementWithDescribe handles SHOW statements including DESCRIBE
func (e *SQLEngine) executeShowStatementWithDescribe(ctx context.Context, stmt *ShowStatement) (*QueryResult, error) {
switch strings.ToUpper(stmt.Type) {
case "DATABASES":
return e.showDatabases(ctx)
case "TABLES":
// Parse FROM clause for database specification, or use current database context
database := ""
// Check if there's a database specified in SHOW TABLES FROM database
if stmt.Schema != "" {
// Use schema field if set by parser
database = stmt.Schema
} else {
// Try to get from OnTable.Name with proper nil checks
if stmt.OnTable.Name != nil {
if nameStr := stmt.OnTable.Name.String(); nameStr != "" {
database = nameStr
} else {
database = e.catalog.GetCurrentDatabase()
}
} else {
database = e.catalog.GetCurrentDatabase()
}
}
if database == "" {
// Use current database context
database = e.catalog.GetCurrentDatabase()
}
return e.showTables(ctx, database)
case "COLUMNS":
// SHOW COLUMNS FROM table is equivalent to DESCRIBE
var tableName, database string
// Safely extract table name and database with proper nil checks
if stmt.OnTable.Name != nil {
tableName = stmt.OnTable.Name.String()
if stmt.OnTable.Qualifier != nil {
database = stmt.OnTable.Qualifier.String()
}
}
if tableName != "" {
return e.executeDescribeStatement(ctx, tableName, database)
}
fallthrough
default:
err := fmt.Errorf("unsupported SHOW statement: %s", stmt.Type)
return &QueryResult{Error: err}, err
}
}
|
