Method parsePivot

core/src/main/java/io/questdb/griffin/SqlParser.java:3888–4066

Parses PIVOT clause with the following syntax: PIVOT ( agg_func(col) [AS alias], ... FOR pivot_col IN (val1 [AS alias1], val2 [AS alias2], ... | subquery) [FOR pivot_col2 IN (...)] [GROUP BY col1, col2, ...] ) [alias] Note: ELSE clause is not supported in PIVO

(GenericLexer lexer, IQueryModel model, SqlParserCallback sqlParserCallback)

     * do not support ELSE in PIVOT. For such requirements, user can use subqueries instead.
     */
    private CharSequence parsePivot(GenericLexer lexer, IQueryModel model, SqlParserCallback sqlParserCallback) throws SqlException {
        CharSequence tok;
        expectTok(lexer, '(');

        // Parse aggregate functions.
        FunctionFactoryCache functionFactoryCache = cairoEngine.getFunctionFactoryCache();
        pivotAliasMap.clear();
        do {
            model.addPivotGroupByColumn(parsePivotAggregateColumn(lexer, model, functionFactoryCache, sqlParserCallback));
            tok = optTok(lexer);
        } while (tok != null && isNotForKeyword(tok) && isComma(tok));

        ObjList<QueryColumn> pivotGroupByCols = model.getPivotGroupByColumns();
        boolean hasNoAlias = false;
        for (int i = 0, n = pivotGroupByCols.size(); i < n; i++) {
            QueryColumn qc = pivotGroupByCols.getQuick(i);
            if (qc.getAlias() == null) {
                hasNoAlias = true;
                CharacterStoreEntry entry = characterStore.newEntry();
                qc.getAst().toSink(entry);
                CharSequence alias = SqlUtil.createExprColumnAlias(
                        characterStore,
                        entry.toImmutable(),
                        pivotAliasMap,
                        aliasSequenceMap,
                        configuration.getColumnAliasGeneratedMaxSize(),
                        true
                );
                pivotAliasMap.add(alias);
                qc.setAlias(alias, qc.getAst().position);
            }
        }
        model.setPivotGroupByColumnHasNoAlias(hasNoAlias && pivotGroupByCols.size() == 1);

        if (tok == null || isNotForKeyword(tok)) {
            throw SqlException.$(lexer.lastTokenPosition(), "expected FOR");
        }

        // Parse FOR expressions (e.g., FOR region IN ('East', 'West') ELSE 'Other')
        // We parse "col IN (values)" separately (not as standard IN expression) because
        // PIVOT supports per-value aliases (e.g., 'value' AS alias) which regular IN doesn't.
        while (true) {
            ExpressionNode inColumnExpr;
            try {
                // Stop at top-level IN operator to handle values list with alias support
                expressionParser.setStopOnTopINOperator(true);
                inColumnExpr = expr(lexer, model, sqlParserCallback);
            } finally {
                expressionParser.setStopOnTopINOperator(false);
            }
            if (inColumnExpr == null) {
                throw SqlException.$(lexer.lastTokenPosition(), "expected IN expression");
            }
            if (hasGroupByFunc(sqlNodeStack, functionFactoryCache, inColumnExpr)) {
                throw SqlException.$(inColumnExpr.position, "aggregate functions are not supported in PIVOT FOR expressions");
            }

            expectTok(lexer, "in");