github.com/cockroachdb/cockroach@v20.2.0-alpha.1+incompatible/pkg/sql/delegate/delegate.go (about)

     1  // Copyright 2019 The Cockroach Authors.
     2  //
     3  // Use of this software is governed by the Business Source License
     4  // included in the file licenses/BSL.txt.
     5  //
     6  // As of the Change Date specified in that file, in accordance with
     7  // the Business Source License, use of this software will be governed
     8  // by the Apache License, Version 2.0, included in the file
     9  // licenses/APL.txt.
    10  
    11  package delegate
    12  
    13  import (
    14  	"context"
    15  
    16  	"github.com/cockroachdb/cockroach/pkg/sql/opt/cat"
    17  	"github.com/cockroachdb/cockroach/pkg/sql/parser"
    18  	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
    19  	"github.com/cockroachdb/cockroach/pkg/util/errorutil/unimplemented"
    20  )
    21  
    22  // Certain statements (most SHOW variants) are just syntactic sugar for a more
    23  // complicated underlying query.
    24  //
    25  // This package contains the logic to convert the AST of such a statement to the
    26  // AST of the equivalent query to be planned.
    27  
    28  // TryDelegate takes a statement and checks if it is one of the statements that
    29  // can be rewritten as a lower level query. If it can, returns a new AST which
    30  // is equivalent to the original statement. Otherwise, returns nil.
    31  func TryDelegate(
    32  	ctx context.Context, catalog cat.Catalog, evalCtx *tree.EvalContext, stmt tree.Statement,
    33  ) (tree.Statement, error) {
    34  	d := delegator{
    35  		ctx:     ctx,
    36  		catalog: catalog,
    37  		evalCtx: evalCtx,
    38  	}
    39  	switch t := stmt.(type) {
    40  	case *tree.ShowClusterSettingList:
    41  		return d.delegateShowClusterSettingList(t)
    42  
    43  	case *tree.ShowDatabases:
    44  		return d.delegateShowDatabases(t)
    45  
    46  	case *tree.ShowCreate:
    47  		return d.delegateShowCreate(t)
    48  
    49  	case *tree.ShowDatabaseIndexes:
    50  		return d.delegateShowDatabaseIndexes(t)
    51  
    52  	case *tree.ShowIndexes:
    53  		return d.delegateShowIndexes(t)
    54  
    55  	case *tree.ShowColumns:
    56  		return d.delegateShowColumns(t)
    57  
    58  	case *tree.ShowConstraints:
    59  		return d.delegateShowConstraints(t)
    60  
    61  	case *tree.ShowPartitions:
    62  		return d.delegateShowPartitions(t)
    63  
    64  	case *tree.ShowGrants:
    65  		return d.delegateShowGrants(t)
    66  
    67  	case *tree.ShowJobs:
    68  		return d.delegateShowJobs(t)
    69  
    70  	case *tree.ShowQueries:
    71  		return d.delegateShowQueries(t)
    72  
    73  	case *tree.ShowRanges:
    74  		return d.delegateShowRanges(t)
    75  
    76  	case *tree.ShowRangeForRow:
    77  		return d.delegateShowRangeForRow(t)
    78  
    79  	case *tree.ShowRoleGrants:
    80  		return d.delegateShowRoleGrants(t)
    81  
    82  	case *tree.ShowRoles:
    83  		return d.delegateShowRoles()
    84  
    85  	case *tree.ShowSchemas:
    86  		return d.delegateShowSchemas(t)
    87  
    88  	case *tree.ShowSequences:
    89  		return d.delegateShowSequences(t)
    90  
    91  	case *tree.ShowSessions:
    92  		return d.delegateShowSessions(t)
    93  
    94  	case *tree.ShowSyntax:
    95  		return d.delegateShowSyntax(t)
    96  
    97  	case *tree.ShowTables:
    98  		return d.delegateShowTables(t)
    99  
   100  	case *tree.ShowUsers:
   101  		return d.delegateShowRoles()
   102  
   103  	case *tree.ShowVar:
   104  		return d.delegateShowVar(t)
   105  
   106  	case *tree.ShowZoneConfig:
   107  		return d.delegateShowZoneConfig(t)
   108  
   109  	case *tree.ShowTransactionStatus:
   110  		return d.delegateShowVar(&tree.ShowVar{Name: "transaction_status"})
   111  
   112  	case *tree.ShowSavepointStatus:
   113  		return nil, unimplemented.NewWithIssue(47333, "cannot use SHOW SAVEPOINT STATUS as a statement source")
   114  
   115  	default:
   116  		return nil, nil
   117  	}
   118  }
   119  
   120  type delegator struct {
   121  	ctx     context.Context
   122  	catalog cat.Catalog
   123  	evalCtx *tree.EvalContext
   124  }
   125  
   126  func parse(sql string) (tree.Statement, error) {
   127  	s, err := parser.ParseOne(sql)
   128  	return s.AST, err
   129  }