Support series expressions, i.e. a series of expressions
authorscottmk <scottmk@dcc99617-32d9-48b4-a31d-7c20da2025e4>
Fri, 28 May 2010 01:46:29 +0000 (01:46 +0000)
committerscottmk <scottmk@dcc99617-32d9-48b4-a31d-7c20da2025e4>
Fri, 28 May 2010 01:46:29 +0000 (01:46 +0000)
separated by operators or commas.  This construct will
be especially useful for chains of ANDs or ORs.

M    Open-ILS/include/openils/oils_buildq.h
M    Open-ILS/src/c-apps/oils_storedq.c
M    Open-ILS/src/c-apps/buildSQL.c

git-svn-id: svn://svn.open-ils.org/ILS/trunk@16526 dcc99617-32d9-48b4-a31d-7c20da2025e4

Open-ILS/include/openils/oils_buildq.h
Open-ILS/src/c-apps/buildSQL.c
Open-ILS/src/c-apps/oils_storedq.c

index 42ea5f1..6f25490 100644 (file)
@@ -158,6 +158,7 @@ typedef enum {
        EXP_NULL,
        EXP_NUMBER,
        EXP_OPERATOR,
        EXP_NULL,
        EXP_NUMBER,
        EXP_OPERATOR,
+    EXP_SERIES,
        EXP_STRING,
        EXP_SUBQUERY
 } ExprType;
        EXP_STRING,
        EXP_SUBQUERY
 } ExprType;
@@ -181,6 +182,7 @@ struct Expression_ {
        int         cast_type_id;
        int         negate;             // Boolean
        BindVar*    bind;
        int         cast_type_id;
        int         negate;             // Boolean
        BindVar*    bind;
+       Expression* subexp_list;        // Linked list of subexpressions
 };
 
 struct QSeq_ {
 };
 
 struct QSeq_ {
@@ -217,7 +219,7 @@ void storedQFree( StoredQ* sq );
 
 void storedQCleanup( void );
 
 
 void storedQCleanup( void );
 
-int buildSQL( BuildSQLState* state, StoredQ* query );
+int buildSQL( BuildSQLState* state, const StoredQ* query );
 
 void oilsStoredQSetVerbose( void );
 
 
 void oilsStoredQSetVerbose( void );
 
@@ -227,7 +229,7 @@ jsonObject* oilsNextRow( BuildSQLState* state );
 
 jsonObject* oilsBindVarList( osrfHash* bindvar_list );
 
 
 jsonObject* oilsBindVarList( osrfHash* bindvar_list );
 
-int oilsApplyBindValues( BuildSQLState* state, jsonObject* bindings );
+int oilsApplyBindValues( BuildSQLState* state, const jsonObject* bindings );
 
 #ifdef __cplusplus
 }
 
 #ifdef __cplusplus
 }
index 0951074..3fcf85e 100644 (file)
 #include "openils/oils_sql.h"
 #include "openils/oils_buildq.h"
 
 #include "openils/oils_sql.h"
 #include "openils/oils_buildq.h"
 
-static void build_Query( BuildSQLState* state, StoredQ* query );
-static void buildCombo( BuildSQLState* state, StoredQ* query, const char* type_str );
-static void buildSelect( BuildSQLState* state, StoredQ* query );
-static void buildFrom( BuildSQLState* state, FromRelation* core_from );
-static void buildJoin( BuildSQLState* state, FromRelation* join );
-static void buildSelectList( BuildSQLState* state, SelectItem* item );
-static void buildOrderBy( BuildSQLState* state, OrderItem* ord_list );
-static void buildExpression( BuildSQLState* state, Expression* expr );
-static void buildBindVar( BuildSQLState* state, BindVar* bind );
+static void build_Query( BuildSQLState* state, const StoredQ* query );
+static void buildCombo( BuildSQLState* state, const StoredQ* query, const char* type_str );
+static void buildSelect( BuildSQLState* state, const StoredQ* query );
+static void buildFrom( BuildSQLState* state, const FromRelation* core_from );
+static void buildJoin( BuildSQLState* state, const FromRelation* join );
+static void buildSelectList( BuildSQLState* state, const SelectItem* item );
+static void buildOrderBy( BuildSQLState* state, const OrderItem* ord_list );
+static void buildExpression( BuildSQLState* state, const Expression* expr );
+static void buildSeries( BuildSQLState* state, const Expression* subexp_list, const char* op );
+static void buildBindVar( BuildSQLState* state, const BindVar* bind );
 static void buildScalar( BuildSQLState* state, int numeric, const jsonObject* obj );
 
 static void add_newline( BuildSQLState* state );
 static void buildScalar( BuildSQLState* state, int numeric, const jsonObject* obj );
 
 static void add_newline( BuildSQLState* state );
@@ -111,7 +112,7 @@ jsonObject* oilsBindVarList( osrfHash* bindvar_list ) {
        The @a bindings parameter must be a JSON_HASH.  The keys are the names of bind variables.
        The values are the corresponding values for the variables.
 */
        The @a bindings parameter must be a JSON_HASH.  The keys are the names of bind variables.
        The values are the corresponding values for the variables.
 */
-int oilsApplyBindValues( BuildSQLState* state, jsonObject* bindings ) {
+int oilsApplyBindValues( BuildSQLState* state, const jsonObject* bindings ) {
        if( !state ) {
                osrfLogError( OSRF_LOG_MARK, "NULL pointer to state" );
                return 1;
        if( !state ) {
                osrfLogError( OSRF_LOG_MARK, "NULL pointer to state" );
                return 1;
@@ -155,7 +156,7 @@ int oilsApplyBindValues( BuildSQLState* state, jsonObject* bindings ) {
 
        Clear the output buffer, call build_Query() to do the work, and add a closing semicolon.
 */
 
        Clear the output buffer, call build_Query() to do the work, and add a closing semicolon.
 */
-int buildSQL( BuildSQLState* state, StoredQ* query ) {
+int buildSQL( BuildSQLState* state, const StoredQ* query ) {
        state->error  = 0;
        buffer_reset( state->sql );
        state->indent = 0;
        state->error  = 0;
        buffer_reset( state->sql );
        state->indent = 0;
@@ -177,7 +178,7 @@ int buildSQL( BuildSQLState* state, StoredQ* query ) {
 
        Look at the query type and branch to the corresponding routine.
 */
 
        Look at the query type and branch to the corresponding routine.
 */
-static void build_Query( BuildSQLState* state, StoredQ* query ) {
+static void build_Query( BuildSQLState* state, const StoredQ* query ) {
        if( buffer_length( state->sql ))
                add_newline( state );
 
        if( buffer_length( state->sql ))
                add_newline( state );
 
@@ -209,7 +210,7 @@ static void build_Query( BuildSQLState* state, StoredQ* query ) {
        @param query Pointer to the query to be built.
        @param type_str The query type, as a string.
 */
        @param query Pointer to the query to be built.
        @param type_str The query type, as a string.
 */
-static void buildCombo( BuildSQLState* state, StoredQ* query, const char* type_str ) {
+static void buildCombo( BuildSQLState* state, const StoredQ* query, const char* type_str ) {
 
        QSeq* seq = query->child_list;
        if( !seq ) {
 
        QSeq* seq = query->child_list;
        if( !seq ) {
@@ -246,7 +247,7 @@ static void buildCombo( BuildSQLState* state, StoredQ* query, const char* type_s
        @param state Pointer to the query-building context.
        @param query Pointer to the StoredQ structure that represents the query.
 */
        @param state Pointer to the query-building context.
        @param query Pointer to the StoredQ structure that represents the query.
 */
-static void buildSelect( BuildSQLState* state, StoredQ* query ) {
+static void buildSelect( BuildSQLState* state, const StoredQ* query ) {
 
        FromRelation* from_clause = query->from_clause;
        if( !from_clause ) {
 
        FromRelation* from_clause = query->from_clause;
        if( !from_clause ) {
@@ -330,7 +331,7 @@ static void buildSelect( BuildSQLState* state, StoredQ* query ) {
        @param Pointer to the query-building context.
        @param Pointer to the StoredQ query to which the FROM clause belongs.
 */
        @param Pointer to the query-building context.
        @param Pointer to the StoredQ query to which the FROM clause belongs.
 */
-static void buildFrom( BuildSQLState* state, FromRelation* core_from ) {
+static void buildFrom( BuildSQLState* state, const FromRelation* core_from ) {
 
        add_newline( state );
        buffer_add( state->sql, "FROM" );
 
        add_newline( state );
        buffer_add( state->sql, "FROM" );
@@ -401,7 +402,7 @@ static void buildFrom( BuildSQLState* state, FromRelation* core_from ) {
        decr_indent( state );
 }
 
        decr_indent( state );
 }
 
-static void buildJoin( BuildSQLState* state, FromRelation* join ) {
+static void buildJoin( BuildSQLState* state, const FromRelation* join ) {
        add_newline( state );
        switch( join->join_type ) {
                case JT_NONE :
        add_newline( state );
        switch( join->join_type ) {
                case JT_NONE :
@@ -494,7 +495,12 @@ static void buildJoin( BuildSQLState* state, FromRelation* join ) {
        }
 }
 
        }
 }
 
-static void buildSelectList( BuildSQLState* state, SelectItem* item ) {
+/**
+       @brief Build a SELECT list.
+       @param state Pointer to the query-building context.
+       @param item Pointer to the first in a linked list of SELECT items.
+*/
+static void buildSelectList( BuildSQLState* state, const SelectItem* item ) {
 
        int first = 1;
        while( item ) {
 
        int first = 1;
        while( item ) {
@@ -524,7 +530,7 @@ static void buildSelectList( BuildSQLState* state, SelectItem* item ) {
        @param state Pointer to the query-building context.
        @param ord_list Pointer to the first node in a linked list of OrderItems.
 */
        @param state Pointer to the query-building context.
        @param ord_list Pointer to the first node in a linked list of OrderItems.
 */
-static void buildOrderBy( BuildSQLState* state, OrderItem* ord_list ) {
+static void buildOrderBy( BuildSQLState* state, const OrderItem* ord_list ) {
        add_newline( state );
        buffer_add( state->sql, "ORDER BY" );
        incr_indent( state );
        add_newline( state );
        buffer_add( state->sql, "ORDER BY" );
        incr_indent( state );
@@ -554,7 +560,7 @@ static void buildOrderBy( BuildSQLState* state, OrderItem* ord_list ) {
        @param state Pointer to the query-building context.
        @param expr Pointer to the Expression representing the expression to be built.
 */
        @param state Pointer to the query-building context.
        @param expr Pointer to the Expression representing the expression to be built.
 */
-static void buildExpression( BuildSQLState* state, Expression* expr ) {
+static void buildExpression( BuildSQLState* state, const Expression* expr ) {
        if( !expr ) {
                osrfLogError( OSRF_LOG_MARK, sqlAddMsg( state,
                        "Internal error: NULL pointer to Expression" ));
        if( !expr ) {
                osrfLogError( OSRF_LOG_MARK, sqlAddMsg( state,
                        "Internal error: NULL pointer to Expression" ));
@@ -732,6 +738,19 @@ static void buildExpression( BuildSQLState* state, Expression* expr ) {
                                buffer_add_char( state->sql, ')' );
 
                        break;
                                buffer_add_char( state->sql, ')' );
 
                        break;
+               case EXP_SERIES :
+                       if( expr->negate )
+                               buffer_add( state->sql, "NOT (" );
+
+                       buildSeries( state, expr->subexp_list, expr->op );
+                       if( state->error ) {
+                               sqlAddMsg( state, "Unable to build series expression using operator \"%s\"",
+                                       expr->op ? expr->op : "," );
+                       }
+                       if( expr->negate )
+                               buffer_add_char( state->sql, ')' );
+
+                       break;
                case EXP_STRING :                     // String literal
                        if( !expr->literal ) {
                                osrfLogWarning( OSRF_LOG_MARK, sqlAddMsg( state,
                case EXP_STRING :                     // String literal
                        if( !expr->literal ) {
                                osrfLogWarning( OSRF_LOG_MARK, sqlAddMsg( state,
@@ -768,6 +787,52 @@ static void buildExpression( BuildSQLState* state, Expression* expr ) {
 }
 
 /**
 }
 
 /**
+       @brief Build a series of expressions separated by a specified operator, or by commas.
+       @param state Pointer to the query-building context.
+       @param subexp_list Pointer to the first Expression in a linked list.
+       @param op Pointer to the operator, or NULL for commas.
+
+       If the operator is AND or OR (in upper, lower, or mixed case), the second and all
+       subsequent operators will begin on a new line.
+*/
+static void buildSeries( BuildSQLState* state, const Expression* subexp_list, const char* op ) {
+
+       int comma = 0;             // Boolean; true if separator is a comma
+       int newline_needed = 0;    // Boolean; true if operator is AND or OR
+
+       if( !op ) {
+               op = ",";
+               comma = 1;
+       } else if( !strcmp( op, "," ))
+               comma = 1;
+       else if( !strcasecmp( op, "AND" ) || !strcasecmp( op, "OR" ))
+               newline_needed = 1;
+
+       int first = 1;               // Boolean; true for first item in list
+       while( subexp_list ) {
+               if( first )
+                       first = 0;   // No separator needed yet
+               else {
+                       // Insert a separator
+                       if( comma )
+                               buffer_add( state->sql, ", " );
+                       else {
+                               if( newline_needed )
+                                       add_newline( state );
+                               else
+                                       buffer_add_char( state->sql, ' ' );
+
+                               buffer_add( state->sql, op );
+                               buffer_add_char( state->sql, ' ' );
+                       }
+               }
+
+               buildExpression( state, subexp_list );
+               subexp_list = subexp_list->next;
+       }
+}
+
+/**
        @brief Add the value of a bind variable to an SQL statement.
        @param state Pointer to the query-building context.
        @param bind Pointer to the bind variable whose value is to be added to the SQL.
        @brief Add the value of a bind variable to an SQL statement.
        @param state Pointer to the query-building context.
        @param bind Pointer to the bind variable whose value is to be added to the SQL.
@@ -775,7 +840,7 @@ static void buildExpression( BuildSQLState* state, Expression* expr ) {
        The value may be a null, a scalar, or an array of nulls and/or scalars, depending on
        the type of the bind variable.
 */
        The value may be a null, a scalar, or an array of nulls and/or scalars, depending on
        the type of the bind variable.
 */
-static void buildBindVar( BuildSQLState* state, BindVar* bind ) {
+static void buildBindVar( BuildSQLState* state, const BindVar* bind ) {
 
        // Decide where to get the value, if any
        const jsonObject* value = NULL;
 
        // Decide where to get the value, if any
        const jsonObject* value = NULL;
@@ -902,6 +967,10 @@ static void buildScalar( BuildSQLState* state, int numeric, const jsonObject* ob
        }
 }
 
        }
 }
 
+/**
+       @brief Start a new line in the output, with the current level of indentation.
+       @param state Pointer to the query-building context.
+*/
 static void add_newline( BuildSQLState* state ) {
        buffer_add_char( state->sql, '\n' );
 
 static void add_newline( BuildSQLState* state ) {
        buffer_add_char( state->sql, '\n' );
 
@@ -917,10 +986,18 @@ static void add_newline( BuildSQLState* state ) {
        }
 }
 
        }
 }
 
+/**
+       @brief Increase the degree of indentation.
+       @param state Pointer to the query-building context.
+*/
 static inline void incr_indent( BuildSQLState* state ) {
        ++state->indent;
 }
 
 static inline void incr_indent( BuildSQLState* state ) {
        ++state->indent;
 }
 
+/**
+       @brief Reduce the degree of indentation.
+       @param state Pointer to the query-building context.
+*/
 static inline void decr_indent( BuildSQLState* state ) {
        if( state->indent )
                --state->indent;
 static inline void decr_indent( BuildSQLState* state ) {
        if( state->indent )
                --state->indent;
index 6fb9769..3b01840 100644 (file)
@@ -43,7 +43,9 @@ static void bindVarFree( char* name, void* p );
 
 static Expression* getExpression( BuildSQLState* state, int id );
 static Expression* constructExpression( BuildSQLState* state, dbi_result result );
 
 static Expression* getExpression( BuildSQLState* state, int id );
 static Expression* constructExpression( BuildSQLState* state, dbi_result result );
+static void expressionListFree( Expression* exp );
 static void expressionFree( Expression* exp );
 static void expressionFree( Expression* exp );
+static Expression* getExpressionList( BuildSQLState* state, int id );
 
 static OrderItem* getOrderByList( BuildSQLState* state, int query_id );
 static OrderItem* constructOrderItem( BuildSQLState* state, dbi_result result );
 
 static OrderItem* getOrderByList( BuildSQLState* state, int query_id );
 static OrderItem* constructOrderItem( BuildSQLState* state, dbi_result result );
@@ -119,6 +121,7 @@ StoredQ* getStoredQuery( BuildSQLState* state, int query_id ) {
                osrfLogError( OSRF_LOG_MARK, sqlAddMsg( state, 
                        "Unable to query query.stored_query table: #%d %s",
                        errnum, msg ? msg : "No description available" ));
                osrfLogError( OSRF_LOG_MARK, sqlAddMsg( state, 
                        "Unable to query query.stored_query table: #%d %s",
                        errnum, msg ? msg : "No description available" ));
+               state->error = 1;
        }
 
        pop_id( &state->query_stack );
        }
 
        pop_id( &state->query_stack );
@@ -503,6 +506,7 @@ static FromRelation* getFromRelation( BuildSQLState* state, int id ) {
                osrfLogError( OSRF_LOG_MARK, sqlAddMsg( state,
                        "Unable to query query.from_relation table: #%d %s",
                        errnum, msg ? msg : "No description available" ));
                osrfLogError( OSRF_LOG_MARK, sqlAddMsg( state,
                        "Unable to query query.from_relation table: #%d %s",
                        errnum, msg ? msg : "No description available" ));
+               state->error = 1;
        }
 
        if( fr )
        }
 
        if( fr )
@@ -709,6 +713,7 @@ static FromRelation* getJoinList( BuildSQLState* state, int id ) {
                osrfLogError( OSRF_LOG_MARK, sqlAddMsg( state,
                        "Unable to query query.from_relation table for join list: #%d %s",
                        errnum, msg ? msg : "No description available" ));
                osrfLogError( OSRF_LOG_MARK, sqlAddMsg( state,
                        "Unable to query query.from_relation table for join list: #%d %s",
                        errnum, msg ? msg : "No description available" ));
+               state->error = 1;
        }
 
        return join_list;
        }
 
        return join_list;
@@ -795,8 +800,9 @@ static SelectItem* getSelectList( BuildSQLState* state, int query_id ) {
                const char* msg;
                int errnum = dbi_conn_error( state->dbhandle, &msg );
                osrfLogError( OSRF_LOG_MARK, sqlAddMsg( state,
                const char* msg;
                int errnum = dbi_conn_error( state->dbhandle, &msg );
                osrfLogError( OSRF_LOG_MARK, sqlAddMsg( state,
-                                         "Unable to query query.select_list table: #%d %s",
-                                         errnum, msg ? msg : "No description available" ));
+                       "Unable to query query.select_list table: #%d %s",
+                       errnum, msg ? msg : "No description available" ));
+               state->error = 1;
        }
 
        return select_list;
        }
 
        return select_list;
@@ -917,6 +923,7 @@ static BindVar* getBindVar( BuildSQLState* state, const char* name ) {
                osrfLogError( OSRF_LOG_MARK, sqlAddMsg( state,
                        "Unable to query query.bind_variable table for \"%s\": #%d %s",
                        name, errnum, msg ? msg : "No description available" ));
                osrfLogError( OSRF_LOG_MARK, sqlAddMsg( state,
                        "Unable to query query.bind_variable table for \"%s\": #%d %s",
                        name, errnum, msg ? msg : "No description available" ));
+               state->error = 1;
        }
 
        if( bind ) {
        }
 
        if( bind ) {
@@ -1068,6 +1075,7 @@ static Expression* getExpression( BuildSQLState* state, int id ) {
                osrfLogError( OSRF_LOG_MARK, sqlAddMsg( state,
                        "Unable to query query.expression table: #%d %s",
                        errnum, msg ? msg : "No description available" ));
                osrfLogError( OSRF_LOG_MARK, sqlAddMsg( state,
                        "Unable to query query.expression table: #%d %s",
                        errnum, msg ? msg : "No description available" ));
+               state->error = 1;
        }
 
        pop_id( &state->expr_stack );
        }
 
        pop_id( &state->expr_stack );
@@ -1116,6 +1124,8 @@ static Expression* constructExpression( BuildSQLState* state, dbi_result result
                type = EXP_NUMBER;
        else if( !strcmp( type_str, "xop" ))
                type = EXP_OPERATOR;
                type = EXP_NUMBER;
        else if( !strcmp( type_str, "xop" ))
                type = EXP_OPERATOR;
+       else if( !strcmp( type_str, "xser" ))
+               type = EXP_SERIES;
        else if( !strcmp( type_str, "xstr" ))
                type = EXP_STRING;
        else if( !strcmp( type_str, "xsubq" ))
        else if( !strcmp( type_str, "xstr" ))
                type = EXP_STRING;
        else if( !strcmp( type_str, "xsubq" ))
@@ -1175,6 +1185,7 @@ static Expression* constructExpression( BuildSQLState* state, dbi_result result
        Expression* right_operand = NULL;
        StoredQ* subquery = NULL;
        BindVar* bind = NULL;
        Expression* right_operand = NULL;
        StoredQ* subquery = NULL;
        BindVar* bind = NULL;
+       Expression* subexp_list = NULL;
 
        if( EXP_OPERATOR == type ) {
                // Load left and/or right operands
 
        if( EXP_OPERATOR == type ) {
                // Load left and/or right operands
@@ -1268,6 +1279,14 @@ static Expression* constructExpression( BuildSQLState* state, dbi_result result
                                return NULL;
                        }
                }
                                return NULL;
                        }
                }
+       } else if( EXP_SERIES == type ) {
+               subexp_list = getExpressionList( state, id );
+               if( state->error ) {
+                       osrfLogWarning( OSRF_LOG_MARK, sqlAddMsg( state,
+                               "Unable to get subexpressions for expression series using operator \"%s\"",
+                                       operator ? operator : "," ));
+                       return NULL;
+               }
        } else if( EXP_SUBQUERY == type ) {
                if( -1 == subquery_id ) {
                        osrfLogWarning( OSRF_LOG_MARK, sqlAddMsg( state,
        } else if( EXP_SUBQUERY == type ) {
                if( -1 == subquery_id ) {
                        osrfLogWarning( OSRF_LOG_MARK, sqlAddMsg( state,
@@ -1339,15 +1358,29 @@ static Expression* constructExpression( BuildSQLState* state, dbi_result result
        exp->cast_type_id = subquery_id;
        exp->negate = negate;
        exp->bind = bind;
        exp->cast_type_id = subquery_id;
        exp->negate = negate;
        exp->bind = bind;
+       exp->subexp_list = subexp_list;
 
        return exp;
 }
 
 /**
 
        return exp;
 }
 
 /**
+       @brief Free all the Expressions in a linked list of Expressions.
+       @param exp Pointer to the first Expression in the list.
+*/
+static void expressionListFree( Expression* exp ) {
+       while( exp ) {
+               Expression* next = exp->next;
+               expressionFree( exp );
+               exp = next;
+       }
+}
+
+/**
        @brief Deallocate an Expression.
        @param exp Pointer to the Expression to be deallocated.
 
        @brief Deallocate an Expression.
        @param exp Pointer to the Expression to be deallocated.
 
-       Free the strings owned by the Expression.  Put the Expressions itself into a free list.
+       Free the strings owned by the Expression.  Put the Expression itself, and any
+       subexpressions that it owns, into a free list.
 */
 static void expressionFree( Expression* exp ) {
        if( exp ) {
 */
 static void expressionFree( Expression* exp ) {
        if( exp ) {
@@ -1371,9 +1404,16 @@ static void expressionFree( Expression* exp ) {
                        storedQFree( exp->subquery );
                        exp->subquery = NULL;
                }
                        storedQFree( exp->subquery );
                        exp->subquery = NULL;
                }
+
                // We don't free the bind member here because the Expression doesn't own it;
                // the bindvar_list hash owns it, so that multiple Expressions can reference it.
 
                // We don't free the bind member here because the Expression doesn't own it;
                // the bindvar_list hash owns it, so that multiple Expressions can reference it.
 
+               if( exp->subexp_list ) {
+                       // Free the linked list of subexpressions
+                       expressionListFree( exp->subexp_list );
+                       exp->subexp_list = NULL;
+               }
+
                // Prepend to the free list
                exp->next = free_expression_list;
                free_expression_list = exp;
                // Prepend to the free list
                exp->next = free_expression_list;
                free_expression_list = exp;
@@ -1381,6 +1421,56 @@ static void expressionFree( Expression* exp ) {
 }
 
 /**
 }
 
 /**
+       @brief Build a list of subexpressions.
+       @param state Pointer to the query-building context.
+       @param id ID of the parent Expression.
+       @return A pointer to the first in a linked list of Expressions, if there are any; or
+               NULL if there aren't any, or in case of an error.
+*/
+static Expression* getExpressionList( BuildSQLState* state, int id ) {
+       Expression* exp_list = NULL;
+       
+       // The ORDER BY is in descending order so that we can build the list by adding to
+       // the head, and it will wind up in the right order.
+       dbi_result result = dbi_conn_queryf( state->dbhandle,
+               "SELECT id, type, parenthesize, parent_expr, seq_no, literal, table_alias, column_name, "
+               "left_operand, operator, right_operand, function_id, subquery, cast_type, negate, "
+               "bind_variable "
+               "FROM query.expression WHERE parent_expr = %d "
+               "ORDER BY seq_no desc;", id );
+
+       if( result ) {
+               if( dbi_result_first_row( result ) ) {
+                       while( 1 ) {
+                               Expression* exp = constructExpression( state, result );
+                               if( exp ) {
+                                       PRINT( "Found a subexpression\n" );
+                                       exp->next = exp_list;
+                                       exp_list  = exp;
+                               } else {
+                                       osrfLogError( OSRF_LOG_MARK, sqlAddMsg( state,
+                                               "Unable to build subexpression list for expression id #%d", id ));
+                                       expressionListFree( exp_list );
+                                       exp_list = NULL;
+                                       break;
+                               }
+                               if( !dbi_result_next_row( result ) )
+                                       break;
+                       };
+               }
+       } else {
+               const char* msg;
+               int errnum = dbi_conn_error( state->dbhandle, &msg );
+               osrfLogError( OSRF_LOG_MARK, sqlAddMsg( state,
+                       "Unable to query query.expression table for expression list: #%d %s",
+                       errnum, msg ? msg : "No description available" ));
+               state->error = 1;
+       }
+
+       return exp_list;
+}
+
+/**
        @brief Build a list of ORDER BY items as a linked list of OrderItems.
        @param state Pointer to the query-building context.
        @param query_id ID for the query to which the ORDER BY belongs.
        @brief Build a list of ORDER BY items as a linked list of OrderItems.
        @param state Pointer to the query-building context.
        @param query_id ID for the query to which the ORDER BY belongs.
@@ -1422,6 +1512,7 @@ static OrderItem* getOrderByList( BuildSQLState* state, int query_id ) {
                osrfLogError( OSRF_LOG_MARK, sqlAddMsg( state,
                        "Unable to query query.order_by_list table: #%d %s",
                        errnum, msg ? msg : "No description available" ));
                osrfLogError( OSRF_LOG_MARK, sqlAddMsg( state,
                        "Unable to query query.order_by_list table: #%d %s",
                        errnum, msg ? msg : "No description available" ));
+               state->error = 1;
        }
 
        return ord_list;
        }
 
        return ord_list;