Ejemplo n.º 1
0
        public SqlSectionExpr Postprocess()
        {
            switch (sectionName)
            {
            case "SELECT":
            case "FROM":
                var lst = new Expr[args.Count];
                for (int i = 0; i < args.Count; i++)
                {
                    var  expr = args[i];
                    var  seq  = expr as SequenceExpr;
                    Expr item;
                    if (seq != null && seq.args.Count > 1)
                    {
                        item = AliasExpr.AsAlias(seq.args) ?? expr;
                    }
                    else
                    {
                        item = expr;
                    }
                    lst[i] = item;
                }
                var res = new SqlSectionExpr(sectionName, lst);
                return(res);

            default:
                return(this);
            }
        }
Ejemplo n.º 2
0
 public bool IsGroupedBy(Dictionary <string, bool> dictGroupBy, AliasExpr r)
 {
     if (dictGroupBy == null)
     {
         return(false);
     }
     else
     {
         return(dictGroupBy.ContainsKey(r.alias) || dictGroupBy.ContainsKey(r.expr.ToString()));
     }
 }
Ejemplo n.º 3
0
        static void SqlFuncsToDDL_Impl(Generator.Ctx ctx, TextWriter wr, TextWriter drops, string locationCode)
        {
            var dictTypes    = new Dictionary <string, ValInf>(StringComparer.OrdinalIgnoreCase);
            var tablesToDrop = new List <string>();

            foreach (var f in ctx.GetFunc(null, 0))
            {
                if (f.xtraAttrs == null || !f.xtraAttrs.TryGetValue(nameof(QueryTemplate), out var objQT))
                {
                    // no QueryTemplate = is not SQL-originated function
                    continue;
                }

                var queryTmpl = (QueryTemplate)objQT;
                var sql       = queryTmpl.SrcSqlExpr;
                var secFrom   = sql[SqlSectionExpr.Kind.From];

                if (secFrom.args.Count > 1)
                {
                    // can't generate DDL for join
                    continue;
                }

                if (f.resultsInfo.All(vi => vi.location != locationCode))
                {
                    // no any output parameter from specified location/origin/source
                    continue;
                }

                Attr.TblAttrsFriendlyText(f.xtraAttrs, wr);

                var colAttrs = (IList <Dictionary <Attr.Col, object> >)f.xtraAttrs[nameof(Attr.Tbl._columns_attrs)];

                var secSelect = sql[SqlSectionExpr.Kind.Select];
                var tableName = secFrom.args[0].ToString();

                tablesToDrop.Add(tableName);

                var extraDDL   = new StringBuilder();
                var initValues = new Dictionary <string, object>();
                int nInitRows  = 0;

                wr.WriteLine($"CREATE TABLE {tableName} (");

                var columns = secSelect.args;
                // columns
                for (int i = 0; i < columns.Count; i++)
                {
                    AliasExpr ae; // column is presented as pair of field name and globally unique alias of value
                    {
                        var colExpr = columns[i];
                        ae = colExpr as AliasExpr;

                        // Skip improper fields
                        if (ae == null)
                        {
                            if (colExpr is ReferenceExpr re)
                            {
                                ae = new AliasExpr(re, re);
                            }
                            else
                            {
                                wr.WriteLine($"--???\t{colExpr}");
                                continue;
                            }
                        }
                        switch (ae.left.nodeType)
                        {
                        case ExprType.Reference: break;

                        case ExprType.Constant:
                            wr.WriteLine($"--\t{ae.left}\t{ae.right}");
                            continue;

                        default:
                            wr.WriteLine($"--???\t{ae.left}\t{ae.right}");
                            continue;
                        }
                    }

                    var attrs = colAttrs[i] ?? Attr.Empty;

                    var fieldName  = ae.left.ToString();//.ToUpperInvariant();
                    var fieldAlias = ValueInfo.WithoutParts(ae.right.ToString(), ValueInfo.Part.Location);

                    var descr = attrs.Get(Attr.Col.Description);

                    string type, trail;
                    {
                        bool isPK    = attrs.GetBool(Attr.Col.PK, false);
                        bool notNull = isPK || attrs.GetBool(Attr.Col.NotNull, false);

                        var curr = new ValInf()
                        {
                            sqlType = attrs.GetString(Attr.Col.Type)
                        };

                        var initVals = attrs.Get(Attr.Col.InitValues);
                        if (initVals != null)
                        {
                            initValues.Add(fieldName, initVals);
                            if (initVals is IList lst)
                            {
                                nInitRows = Math.Max(lst.Count, nInitRows);
                            }
                            else if (nInitRows == 0)
                            {
                                nInitRows = 1;
                            }
                        }

                        ValInf valInfByLookupAttr = null;
                        if (attrs.TryGet(Attr.Col.Lookup, out var objLookup))
                        {
                            var masked = ValueInfo.OverrideByMask(fieldAlias, objLookup.ToString());

                            if (!dictTypes.TryGetValue(masked, out valInfByLookupAttr))
                            {
                                var parts = ValueInfo.FourParts(masked);
                                parts[3]           = null; // remove 'units' part
                                masked             = ValueInfo.FromParts(parts);
                                valInfByLookupAttr = dictTypes[masked];
                            }
                        }

                        // Descriptor 'type' in form '_QUANTITY__UNIT'
                        // remove substance and location parts
                        string sDescrType = ValueInfo.WithoutParts(fieldAlias, ValueInfo.Part.Substance, ValueInfo.Part.Location);

                        ValInf valInfExact = null, valInfByType = null;

                        if (valInfByLookupAttr != null ||
                            dictTypes.TryGetValue(fieldAlias, out valInfExact) ||
                            dictTypes.TryGetValue(sDescrType, out valInfByType))
                        {
                            var vi = valInfByLookupAttr ?? valInfExact ?? valInfByType;

                            if (vi.pkTable != null)
                            {
                                if (isPK)
                                {
                                    if (valInfExact != null)
                                    {
                                        wr.WriteLine($"--WARNING! Value named '{fieldAlias}' is already used as PK in table '{vi.pkTable}'");
                                    }
                                }
                                else
                                {   // create foreign key constraint
                                    var hash = $"{tableName}:{fieldAlias}".GetHashCode().ToString("X").Substring(0, 4);
                                    var sPK  = vi.pkTable.Split('_')[0];
                                    if (sPK.StartsWith(tableName))
                                    {
                                        sPK = sPK.Substring(tableName.Length);
                                    }
                                    var fk = string.Format("fk_{0}_{1}",
                                                           (tableName + '_' + sPK).DeLowerVowel(22),
                                                           hash
                                                           );

                                    #region XRef comment (cross reference information)
                                    {
                                        f.xtraAttrs.TryGetValue(nameof(Attr.Tbl.Substance), out var substance);
                                        f.xtraAttrs.TryGetValue(nameof(Attr.Tbl.Description), out var tableDescr);
                                        var tDesc = Attr.OneLineText(tableDescr);
                                        var fDesc = Attr.OneLineText(descr);
                                        extraDDL.AppendLine($"--XRef\t{vi.pkTable}\t{substance}\t{tDesc}\t{tableName}\t{fieldName}\t{fDesc}");
                                    }
                                    #endregion

                                    extraDDL.AppendLine($"ALTER TABLE {tableName} ADD CONSTRAINT {fk} FOREIGN KEY ({fieldName}) REFERENCES {vi.pkTable};");
                                }
                            }

                            if (curr.sqlType == null)
                            {
                                curr = new ValInf()
                                {
                                    firstValue = vi.firstValue, pkField = vi.pkField, pkTable = vi.pkTable, sqlType = vi.sqlType
                                }
                            }
                            ;
                            else
                            {
                                if (curr.sqlType != vi.sqlType && valInfExact != null)
                                {
                                    wr.WriteLine($"--WARNING! Type mismatch for value named '{fieldAlias}', first declaration has type '{vi.sqlType}'");
                                }
                                curr.firstValue = vi.firstValue;
                                curr.pkTable    = vi.pkTable;
                                curr.pkField    = vi.pkField;
                            }
                        }

                        if (valInfByLookupAttr == null && valInfExact == null)
                        {
                            bool noTypeFound = curr.sqlType == null;
                            if (noTypeFound)
                            {
                                var info = ValueInfo.Create(fieldAlias, true);
                                curr.sqlType = info?.quantity.DefaultDimensionUnit.Name ?? fieldAlias;
                                wr.WriteLine($"--WARNING! No SQL-type inferenced for value named '{fieldAlias}' of type '{sDescrType}'");
                            }
                            if (curr.sqlType != null)
                            {
                                if (isPK)
                                {
                                    curr.pkTable = tableName;
                                    curr.pkField = fieldName;
                                    if (initVals is IList lst)
                                    {
                                        curr.firstValue = lst[0];
                                    }
                                    else
                                    {
                                        curr.firstValue = initVals;
                                    }
                                }
                                if (noTypeFound == false)
                                {
                                    if (isPK)
                                    {
                                        dictTypes.Add(fieldAlias, curr);
                                    }
                                    if (!dictTypes.ContainsKey(sDescrType))
                                    {
                                        dictTypes.Add(sDescrType, new ValInf()
                                        {
                                            sqlType = curr.sqlType
                                        });
                                    }
                                }
                            }
                        }

                        object defVal = attrs.Get(Attr.Col.Default);

                        if (isPK)
                        {
                            trail = " NOT NULL PRIMARY KEY";
                        }
                        else if (notNull)
                        {
                            var def = attrs.Get(Attr.Col.Default) ?? curr.firstValue;
                            if (def != null)
                            {
                                trail = $" DEFAULT {new ConstExpr(def)} NOT NULL";
                            }
                            else
                            {
                                trail = " NOT NULL";
                            }
                        }
                        else
                        {
                            trail = null;
                        }

                        type = curr.sqlType;
                    }

                    var typeArgs = attrs.GetString(Attr.Col.TypeArgs);
                    if (!string.IsNullOrEmpty(typeArgs))
                    {
                        typeArgs = '(' + typeArgs + ')';
                    }

                    wr.WriteLine($"\t{fieldName} {type}{typeArgs}{trail},\t--{fieldAlias}\t{Attr.OneLineText(descr)}");
                }

                wr.WriteLine(')');
                wr.WriteLine(';');
                wr.WriteLine();

                if (extraDDL.Length > 0)
                {
                    wr.WriteLine(extraDDL);
                    wr.WriteLine();
                    extraDDL.Clear();
                }

                if (nInitRows > 0)
                {
                    var fields = string.Join(", ", initValues.Keys);
                    for (int i = 0; i < nInitRows; i++)
                    {
                        var vals = initValues.Values.Select(v =>
                        {
                            if (v is IList lst)
                            {
                                return((i < lst.Count) ? lst[i] : null);
                            }
                            else
                            {
                                return(v);
                            }
                        })
                                   .Select(v => new ConstExpr(v))
                                   .Select(v => ((v.value is string) ? "N" : null) + v.ToString());
                        var values = string.Join(", ", vals);
                        wr.WriteLine($"INSERT INTO {tableName} ({fields}) VALUES ({values});");
                    }
                    wr.WriteLine();

                    #region How to add MS SQL descriptions example
                    //declare @CurrentUser sysname;
                    //select @CurrentUser = user_name();
                    //execute sp_addextendedproperty 'MS_Description', 'Табле комент', 'user', @CurrentUser, 'table', 'PipeSysType_CL';
                    //execute sp_addextendedproperty 'MS_Description', 'This is the column comment', 'user', @CurrentUser, 'table', 'TABLE_1', 'column', 'ID'            }
                    #endregion
                }
            }
            if (drops != null)
            {
                tablesToDrop.Reverse();
                foreach (var tableName in tablesToDrop)
                {
                    drops.WriteLine($"DROP TABLE {tableName};");
                }
            }
        }
Ejemplo n.º 4
0
        static IList <Expr> RestructAsSqlSelect(IList <Expr> lst)
        {
            var seq = lst[0] as SequenceExpr;

            if (seq == null)
            {
                return(lst);
            }
            var ref0 = (seq.args.Count > 0) ? seq.args[0] as ReferenceExpr : null;

            if (ref0 == null || string.Compare(ref0.name, "SELECT", StringComparison.InvariantCultureIgnoreCase) != 0)
            {
                return(lst);
            }
            string sectionName        = null;
            string sectionPartialName = string.Empty;
            var    res          = new List <Expr>(lst.Count);
            var    sectionItems = new List <Expr>(lst.Count);

            foreach (var item in lst)
            {
                var se = item as SequenceExpr;
                if (se == null)
                {
                    se = new SequenceExpr(item);
                }
                var argItems = new List <Expr>();
                foreach (var exprArg in se.args)
                {
                    var      expr = exprArg;
                    var      r    = expr as ReferenceExpr;
                    CallExpr ce   = null;
                    if (r == null)
                    {
                        ce = expr as CallExpr;
                        if (ce != null && ce.funcName.Length > 0)
                        {
                            r = new ReferenceExpr(ce.funcName);
                        }
                    }
                    if (r != null)
                    {
                        var s = r.name.ToUpperInvariant();
                        switch (s)
                        {
                        case "SELECT":
                        case "FROM":
                        case "WHERE":
                        case "BY":
                        case "USING":
                            if (argItems.Count > 0)
                            {
                                moveArgsToSection(sectionName, sectionItems, argItems);
                            }
                            if (sectionName != null)
                            {
                                var after = new SqlSectionExpr(sectionName, sectionItems.ToArray()).Postprocess();
                                if (after == null)
                                {
                                    return(null);
                                }
                                res.Add(after);
                            }
                            else if (sectionItems.Count > 0)
                            {
                                res.AddRange(sectionItems);
                            }
                            sectionItems.Clear();
                            if (s == "BY")
                            {
                                sectionName        = sectionPartialName + ' ' + s;
                                sectionPartialName = string.Empty;
                            }
                            else
                            {
                                System.Diagnostics.Trace.Assert(sectionPartialName.Length == 0, "Unknown SQL clause");
                                sectionName = s;
                            }
                            break;

                        case "JOIN":
                        {
                            System.Diagnostics.Trace.Assert(argItems.Count > 0, "No expressions before JOIN");
                            var ae = AliasExpr.AsAlias(argItems);
                            if (ae != null)
                            {
                                argItems.Clear();
                                argItems.Add(ae);
                            }
                            if (sectionPartialName.Length > 0)
                            {
                                argItems.Add(new ReferenceExpr(sectionPartialName));
                            }
                            argItems.Add(new ReferenceExpr(s));
                            if (ae == null)
                            {
                                var tmp = new SequenceExpr(argItems.ToArray());
                                argItems.Clear();
                                argItems.Add(tmp);
                            }
                            sectionPartialName = string.Empty;
                        }
                        break;

                        case "ON":
                        {
                            int i      = argItems.Count - 1;
                            var subseq = new List <Expr>();
                            while (i >= 0)
                            {
                                var exp = argItems[i];
                                var re  = exp as ReferenceExpr;
                                if (re != null && re.name == "JOIN")
                                {
                                    break;
                                }
                                argItems.RemoveAt(i);
                                i--;
                                subseq.Insert(0, exp);
                            }
                            if (subseq.Count > 0)
                            {
                                argItems.Add((Expr)AliasExpr.AsAlias(subseq) ?? new SequenceExpr(subseq));
                            }
                            argItems.Add(new ReferenceExpr(s));
                        }
                        break;

                        case "ORDER":
                        case "GROUP":
                        case "INNER":
                        case "OUTER":
                        case "LEFT":
                        case "RIGHT":
                        case "CROSS":
                        case "FULL":
                            if (sectionPartialName.Length == 0)
                            {
                                sectionPartialName = s;
                            }
                            else
                            {
                                sectionPartialName += ' ' + s;
                            }
                            break;

                        default:
                            if (ce == null)
                            {
                                argItems.Add(r);
                            }
                            r = null;
                            break;
                        }
                        if (ce == null)
                        {
                            continue;
                        }
                        if (r != null)
                        {
                            expr = new CallExpr(string.Empty, ce.args);
                            ce   = null;
                        }
                    }
                    if (ce != null && ce.funcName == string.Empty)
                    {
                        // no need to modify possible aliases in nested queries
                        var items = RestructAsSqlSelect(ce.args);
                        if (items != ce.args)
                        {
                            argItems.Add(CallExpr.Eval(new SequenceExpr(items)));
                        }
                    }
                    else
                    {
                        argItems.Add(expr);
                    }
                }
                moveArgsToSection(sectionName, sectionItems, argItems);
            }
            if (sectionName != null)
            {
                var after = new SqlSectionExpr(sectionName, sectionItems.ToArray()).Postprocess();
                if (after == null)
                {
                    return(null);
                }
                res.Add(after);
            }
            else if (sectionItems.Count > 0)
            {
                res.AddRange(sectionItems);
            }
            return(res.ToArray());
        }
Ejemplo n.º 5
0
        public Expr CreateQueryExpr(Expr andCondition = null, AliasExpr groupBy = null, Expr[] orderBy = null,
                                    Func <AliasExpr, AliasExpr> resultModifier = null, params string[] resultsNames)
        {
            var sections = new List <Expr>(args.Count);

            // select
            Expr[] toSelect;
            var    gba = (groupBy == null) ? null : groupBy.alias;
            // "group by" preprocessing
            Expr newGroupBySection;
            Dictionary <string, bool> presentInGroupBy = null;
            {
                var currGroupBy = this[SqlSectionExpr.Kind.GroupBy];
                if (currGroupBy != null)
                {
                    newGroupBySection = currGroupBy;
                    presentInGroupBy  = GetPresenseDict(currGroupBy.args);
                }
                else if (groupBy != null)
                {
                    newGroupBySection = new SqlSectionExpr(SqlSectionExpr.Kind.GroupBy, groupBy.expr);
                    presentInGroupBy  = GetPresenseDict(new Expr[] { groupBy });
                }
                else
                {
                    newGroupBySection = null;
                }
            }
            // "select"
            bool resultsModified = false;

            if (resultsNames.Length == 0)
            {
                if (resultModifier != null)
                {
                    toSelect = new Expr[results.Length];
                    for (int i = toSelect.Length - 1; i >= 0; i--)
                    {
                        var r = results[i];
                        var s = IsGroupedBy(presentInGroupBy, r) ? r : resultModifier(r);
                        if (r != s)
                        {
                            resultsModified = true;
                        }
                        toSelect[i] = s;
                    }
                }
                else
                {
                    toSelect = results;
                }
            }
            else
            {
                resultModifier  = resultModifier ?? AsIs;
                toSelect        = new Expr[resultsNames.Length];
                resultsModified = true;
                for (int i = toSelect.Length - 1; i >= 0; i--)
                {
                    var r = results[resNdx[resultsNames[i]]];
                    toSelect[i] = IsGroupedBy(presentInGroupBy, r) ? r : resultModifier(r);
                }
            }
            if (resultsModified)
            {
                sections.Add(new SqlSectionExpr(SqlSectionExpr.Kind.Select, toSelect));
            }
            else
            {
                sections.Add(this[SqlSectionExpr.Kind.Select]);
            }
            // from
            sections.Add(this[SqlSectionExpr.Kind.From]);
            // where
            if (andCondition != null)
            {
                sections.Add(new SqlSectionExpr(SqlSectionExpr.Kind.Where, (condition == null) ? andCondition : new BinaryExpr(ExprType.LogicalAnd, condition, andCondition)));
            }
            else if (condition != null)
            {
                sections.Add(this[SqlSectionExpr.Kind.Where]);
            }
            // group by
            if (newGroupBySection != null)
            {
                sections.Add(newGroupBySection);
            }
            // order by
            var thisOrderBy = this[SqlSectionExpr.Kind.OrderBy];

            if (orderBy != null && orderBy.Length > 0)
            {
                if (thisOrderBy != null)
                {
                    var fromQuery = thisOrderBy.args.Where(e =>
                    {
                        var s = e.ToString();
                        return(presentInGroupBy == null || presentInGroupBy.ContainsKey(s));
                    }).ToArray();
                    var presentInOrderBy = GetPresenseDict(fromQuery);

                    orderBy = fromQuery.Concat(orderBy.Where(e =>
                    {
                        var s = e.ToString();
                        return(!presentInOrderBy.ContainsKey(s));
                    })).ToArray();
                }
                sections.Add(new SqlSectionExpr(SqlSectionExpr.Kind.OrderBy, orderBy));
            }
            else if (thisOrderBy != null)
            {
                sections.Add(this[SqlSectionExpr.Kind.OrderBy]);
            }
            //for (int i = 3; i < sql.Length; i++)
            //	if (sql[i] != null)
            //		sections.Add(sql[i]);
            return(new SequenceExpr(sections)); // todo
        }
Ejemplo n.º 6
0
 static AliasExpr AsIs(AliasExpr ae)
 {
     return(ae);
 }
Ejemplo n.º 7
0
        public SqlExpr(IList <Expr> sections, Options opts)
            : base(sections)
        {
            foreach (SqlSectionExpr s in sections)
            {
                sql[(int)s.kind] = s;
            }
            SqlSectionExpr section;

            // FROM: scan sources
            section = this[SqlSectionExpr.Kind.From];
            if (section == null)
            {
                if (!opts.HasFlag(Options.EmptyFromPossible))
                {
                    throw new Generator.Exception($"new SqlExpr(...): nonempty FROM section expected");
                }
                section = new SqlSectionExpr(SqlSectionExpr.Kind.From);
            }
            IDictionary <string, int> srcAlias2Ndx;

            {
                var items = section.args;
                var srcs  = new List <AliasExpr>(items.Count);
                srcAlias2Ndx = new Dictionary <string, int>(items.Count, StringComparer.OrdinalIgnoreCase);
                int i = 0;
                foreach (var item in items)
                {
                    var ae = item as AliasExpr;
                    if (ae != null)
                    {
                        srcAlias2Ndx[ae.alias] = i++;
                        srcs.Add(ae);
                        continue;
                    }
                    var sq = item as SequenceExpr;
                    if (sq != null)
                    {
                        foreach (var it in sq.args)
                        {
                            var tmp = it as AliasExpr;
                            if (tmp != null)
                            {
                                srcAlias2Ndx[tmp.alias] = i++;
                                srcs.Add(tmp);
                            }
                        }
                    }
                    else
                    {
                        var tmp = new AliasExpr(item, item);
                        srcAlias2Ndx[tmp.alias] = i++;
                        srcs.Add(tmp);
                    }
                }
                //System.Diagnostics.Trace.Assert(i <= 32, "No more than 32 sources in FROM supported");
                sources = srcs.ToArray();
            }
            // SELECT: scan results
            section = this[SqlSectionExpr.Kind.Select];
            {
                var items = section.args;
                int n     = items.Count;
                //System.Diagnostics.Trace.Assert(n <= 64, "No more than 64 result columns in SELECT supported");
                results   = new AliasExpr[n];
                resFields = new Expr[n];
                resNdx    = new Dictionary <string, int>(n, StringComparer.OrdinalIgnoreCase);
                //resultUsesSrcs = new uint[n];
                for (int i = 0; i < n; i++)
                {
                    var aliasExpr = items[i] as AliasExpr;
                    if (aliasExpr != null)
                    {   // item in form "expression alias"
                        Expr resField = null;
                        foreach (var srcAlias in aliasExpr.expr.Traverse <BinaryExpr>(e =>
                        {
                            var be = e as BinaryExpr;
                            if (be != null && be.nodeType == ExprType.Fluent)
                            {
                                return(be);
                            }
                            else
                            {
                                return(null);
                            }
                        }))
                        {
                            if (srcAlias == null)
                            {
                                continue;
                            }
                            int j;
                            if (srcAlias2Ndx.TryGetValue(srcAlias.left.ToString(), out j)) // source alias may be to the left of point
                            {
                                //resultUsesSrcs[i] |= (uint)(1 << j);
                                resField = srcAlias;
                            }
                        }
                        //System.Diagnostics.Trace.Assert(resField != null, "No field reference found");
                        resFields[i] = resField ?? aliasExpr.expr;
                        results[i]   = aliasExpr;
                        resNdx.Add(aliasExpr.alias, i);
                        continue;
                    }
                    var binExpr = items[i] as BinaryExpr;
                    if (binExpr != null)
                    {
                        if (binExpr.nodeType == ExprType.Fluent)
                        {   // item in form "tablename.fieldname"
                            resFields[i] = binExpr;
                            results[i]   = new AliasExpr(binExpr, binExpr.right);
                            resNdx.Add(binExpr.right.ToString(), i);
                            continue;
                        }
                    }
                    else
                    {
                        var tmp = items[i] as ReferenceExpr;
                        if (tmp != null)
                        {   // item in form "fieldname"
                            resFields[i] = tmp;
                            results[i]   = new AliasExpr(tmp, tmp);
                            resNdx.Add(tmp.ToString(), i);
                            continue;
                        }
                    }
                    throw new ArgumentException("SELECTed expression must be a simple field reference or have alias", items[i].ToString());
                }
            }
            // WHERE: scan conditions
            section = this[SqlSectionExpr.Kind.Where];
            if (section != null)
            {
                var items = section.args;
                System.Diagnostics.Trace.Assert(items.Count == 1, "Only one condition expression in WHERE supported");
                condition = items[0];
            }
        }