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

     1  // Copyright 2016 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 sqlbase
    12  
    13  import (
    14  	"context"
    15  
    16  	"github.com/cockroachdb/cockroach/pkg/sql/parser"
    17  	"github.com/cockroachdb/cockroach/pkg/sql/sem/transform"
    18  	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
    19  )
    20  
    21  // MakeDefaultExprs returns a slice of the default expressions for the slice
    22  // of input column descriptors, or nil if none of the input column descriptors
    23  // have default expressions.
    24  // The length of the result slice matches the length of the input column descriptors.
    25  // For every column that has no default expression, a NULL expression is reported
    26  // as default.
    27  func MakeDefaultExprs(
    28  	ctx context.Context,
    29  	cols []ColumnDescriptor,
    30  	txCtx *transform.ExprTransformContext,
    31  	evalCtx *tree.EvalContext,
    32  ) ([]tree.TypedExpr, error) {
    33  	// Check to see if any of the columns have DEFAULT expressions. If there
    34  	// are no DEFAULT expressions, we don't bother with constructing the
    35  	// defaults map as the defaults are all NULL.
    36  	haveDefaults := false
    37  	for i := range cols {
    38  		if cols[i].DefaultExpr != nil {
    39  			haveDefaults = true
    40  			break
    41  		}
    42  	}
    43  	if !haveDefaults {
    44  		return nil, nil
    45  	}
    46  
    47  	// Build the default expressions map from the parsed SELECT statement.
    48  	defaultExprs := make([]tree.TypedExpr, 0, len(cols))
    49  	exprStrings := make([]string, 0, len(cols))
    50  	for i := range cols {
    51  		col := &cols[i]
    52  		if col.DefaultExpr != nil {
    53  			exprStrings = append(exprStrings, *col.DefaultExpr)
    54  		}
    55  	}
    56  	exprs, err := parser.ParseExprs(exprStrings)
    57  	if err != nil {
    58  		return nil, err
    59  	}
    60  
    61  	defExprIdx := 0
    62  	semaCtx := tree.MakeSemaContext()
    63  	for i := range cols {
    64  		col := &cols[i]
    65  		if col.DefaultExpr == nil {
    66  			defaultExprs = append(defaultExprs, tree.DNull)
    67  			continue
    68  		}
    69  		expr := exprs[defExprIdx]
    70  		typedExpr, err := tree.TypeCheck(ctx, expr, &semaCtx, col.Type)
    71  		if err != nil {
    72  			return nil, err
    73  		}
    74  		if typedExpr, err = txCtx.NormalizeExpr(evalCtx, typedExpr); err != nil {
    75  			return nil, err
    76  		}
    77  		defaultExprs = append(defaultExprs, typedExpr)
    78  		defExprIdx++
    79  	}
    80  	return defaultExprs, nil
    81  }
    82  
    83  // ProcessDefaultColumns adds columns with DEFAULT to cols if not present
    84  // and returns the defaultExprs for cols.
    85  func ProcessDefaultColumns(
    86  	ctx context.Context,
    87  	cols []ColumnDescriptor,
    88  	tableDesc *ImmutableTableDescriptor,
    89  	txCtx *transform.ExprTransformContext,
    90  	evalCtx *tree.EvalContext,
    91  ) ([]ColumnDescriptor, []tree.TypedExpr, error) {
    92  	cols = processColumnSet(cols, tableDesc, func(col *ColumnDescriptor) bool {
    93  		return col.DefaultExpr != nil
    94  	})
    95  	defaultExprs, err := MakeDefaultExprs(ctx, cols, txCtx, evalCtx)
    96  	return cols, defaultExprs, err
    97  }
    98  
    99  func processColumnSet(
   100  	cols []ColumnDescriptor, tableDesc *ImmutableTableDescriptor, inSet func(*ColumnDescriptor) bool,
   101  ) []ColumnDescriptor {
   102  	colIDSet := make(map[ColumnID]struct{}, len(cols))
   103  	for i := range cols {
   104  		colIDSet[cols[i].ID] = struct{}{}
   105  	}
   106  
   107  	// Add all public or columns in DELETE_AND_WRITE_ONLY state
   108  	// that satisfy the condition.
   109  	writable := tableDesc.WritableColumns()
   110  	for i := range writable {
   111  		col := &writable[i]
   112  		if inSet(col) {
   113  			if _, ok := colIDSet[col.ID]; !ok {
   114  				colIDSet[col.ID] = struct{}{}
   115  				cols = append(cols, *col)
   116  			}
   117  		}
   118  	}
   119  	return cols
   120  }