(gdb) bt
#0  toast_decompress_datum (attr=0x12572e0) at tuptoaster.c:2291
#1  toast_decompress_datum (attr=0x12572e0) at tuptoaster.c:2277
#2  0x00000000004c3b08 in heap_tuple_untoast_attr_slice (attr=<optimized out>, sliceoffset=0, slicelength=-1) at tuptoaster.c:315
#3  0x000000000085c1e5 in pg_detoast_datum_slice (datum=<optimized out>, first=<optimized out>, count=<optimized out>) at fmgr.c:1767
#4  0x0000000000833b7a in text_substring (str=133761519127512, start=0, length=<optimized out>, length_not_specified=<optimized out>) at varlena.c:956
#5  0x0000000000600a5b in ExecInterpExpr (state=0x12549c8, econtext=0x1253728, isnull=<optimized out>) at execExprInterp.c:649
#6  0x000000000061511f in ExecEvalExprSwitchContext (isNull=0x7ffc45db755f, econtext=<optimized out>, state=<optimized out>) at ../../../src/include/executor/executor.h:307
#7  advance_aggregates (aggstate=0x1253500, aggstate=0x1253500) at nodeAgg.c:679
#8  agg_retrieve_direct (aggstate=0x1253500) at nodeAgg.c:1847
#9  ExecAgg (pstate=0x1253500) at nodeAgg.c:1572
#10 0x000000000060371b in ExecProcNode (node=0x1253500) at ../../../src/include/executor/executor.h:239
#11 ExecutePlan (execute_once=<optimized out>, dest=0x12595b8, direction=<optimized out>, numberTuples=0, sendTuples=<optimized out>, operation=CMD_SELECT, use_parallel_mode=<optimized out>, planstate=0x1253500, estate=0x12532c0) at execMain.c:1648
#12 standard_ExecutorRun (queryDesc=0x11be580, direction=<optimized out>, count=0, execute_once=<optimized out>) at execMain.c:365
#13 0x0000000000748b2b in PortalRunSelect (portal=portal@entry=0x12043a0, forward=forward@entry=true, count=0, count@entry=9223372036854775807, dest=dest@entry=0x12595b8) at pquery.c:929
#14 0x0000000000749f00 in PortalRun (portal=portal@entry=0x12043a0, count=count@entry=9223372036854775807, isTopLevel=isTopLevel@entry=true, run_once=run_once@entry=true, dest=dest@entry=0x12595b8, altdest=altdest@entry=0x12595b8, completionTag=0x7ffc45db77e0 "") at pquery.c:770
#15 0x000000000074611f in exec_simple_query (query_string=0x119c820 "select sum(length(substr(a,0))) from t;") at postgres.c:1215
#16 0x000000000074783e in PostgresMain (argc=<optimized out>, argv=argv@entry=0x11c84d0, dbname=<optimized out>, username=<optimized out>) at postgres.c:4249
#17 0x00000000006d75d9 in BackendRun (port=0x11c09e0, port=0x11c09e0) at postmaster.c:4431
#18 BackendStartup (port=0x11c09e0) at postmaster.c:4122
#19 ServerLoop () at postmaster.c:1704
#20 0x00000000006d840c in PostmasterMain (argc=argc@entry=3, argv=argv@entry=0x11963e0) at postmaster.c:1377