Shulou(Shulou.com)05/31 Report--

< innerslot->

Tts_nvalid); * op- > resvalue = innerslot- > tts_ values [attnum]; * op- > resnull = innerslot- > tts_ isnull [attnum]; EEO_NEXT ();} EEO_CASE (EEOP_OUTER_VAR) {int attnum = op- > d.var.attnum / * See EEOP_INNER_VAR comments * / Assert (attnum > = 0 & & attnum

< outerslot->

Tts_nvalid); * op- > resvalue = outerslot- > tts_ values [attnum]; * op- > resnull = outerslot- > tts_ isnull [attnum]; EEO_NEXT ();} EEO_CASE (EEOP_SCAN_VAR) {int attnum = op- > d.var.attnum / * See EEOP_INNER_VAR comments * / Assert (attnum > = 0 & & attnum

< scanslot->

Tts_nvalid); * op- > resvalue = scanslot- > tts_ values [attnum]; * op- > resnull = scanslot- > tts_ isnull [attnum]; EEO_NEXT ();} EEO_CASE (EEOP_INNER_SYSVAR) {int attnum = op- > d.var.attnum; Datum d / * these asserts must match defenses in slot_getattr * / Assert (innerslot- > tts_tuple! = NULL); Assert (innerslot- > tts_tuple! = & (innerslot- > tts_minhdr)) / * heap_getsysattr has sufficient defenses against bad attnums * / d = heap_getsysattr (innerslot- > tts_tuple, attnum, innerslot- > tts_tupleDescriptor, op- > resnull); * op- > resvalue = d; EEO_NEXT () } EEO_CASE (EEOP_OUTER_SYSVAR) {int attnum = op- > d.var.attnum; Datum d; / * these asserts must match defenses in slot_getattr * / Assert (outerslot- > tts_tuple! = NULL); Assert (outerslot- > tts_tuple! = & (outerslot- > tts_minhdr)) / * heap_getsysattr has sufficient defenses against bad attnums * / d = heap_getsysattr (outerslot- > tts_tuple, attnum, outerslot- > tts_tupleDescriptor, op- > resnull); * op- > resvalue = d; EEO_NEXT () } EEO_CASE (EEOP_SCAN_SYSVAR) {int attnum = op- > d.var.attnum; Datum d; / * these asserts must match defenses in slot_getattr * / Assert (scanslot- > tts_tuple! = NULL); Assert (scanslot- > tts_tuple! = & (scanslot- > tts_minhdr)) / * heap_getsysattr has sufficient defenses against bad attnums * / d = heap_getsysattr (scanslot- > tts_tuple, attnum, scanslot- > tts_tupleDescriptor, op- > resnull); * op- > resvalue = d; EEO_NEXT () } EEO_CASE (EEOP_WHOLEROW) {/ * too complex for an inline implementation * / ExecEvalWholeRowVar (state, op, econtext); EEO_NEXT ();} EEO_CASE (EEOP_ASSIGN_INNER_VAR) {int resultnum = op- > d.assign_var.resultnum Int attnum = op- > d.assignboards var.attnum. / * * We do not need CheckVarSlotCompatibility here; that was taken * care of at compilation time. But see EEOP_INNER_VAR comments. * / Assert (attnum > = 0 & & attnum

< innerslot->

Tts_nvalid); resultslot- > tts_ values [resultnum] = innerslot- > tts_ values [attnum]; resultslot- > tts_ isnull [resultnum] = innerslot- > tts_ isnull [attnum]; EEO_NEXT ();} EEO_CASE (EEOP_ASSIGN_OUTER_VAR) {int resultnum = op- > d.assign_var.resultnum Int attnum = op- > d.assignboards var.attnum. / * * We do not need CheckVarSlotCompatibility here; that was taken * care of at compilation time. But see EEOP_INNER_VAR comments. * / Assert (attnum > = 0 & & attnum

< outerslot->

Tts_nvalid); resultslot- > tts_ values [resultnum] = outerslot- > tts_ values [attnum]; resultslot- > tts_ isnull [resultnum] = outerslot- > tts_ isnull [attnum]; EEO_NEXT ();} EEO_CASE (EEOP_ASSIGN_SCAN_VAR) {int resultnum = op- > d.assign_var.resultnum Int attnum = op- > d.assignboards var.attnum. / * * We do not need CheckVarSlotCompatibility here; that was taken * care of at compilation time. But see EEOP_INNER_VAR comments. * / Assert (attnum > = 0 & & attnum

< scanslot->

Tts_nvalid); resultslot- > tts_ values [resultnum] = scanslot- > tts_ values [attnum]; resultslot- > tts_ isnull [resultnum] = scanslot- > tts_ isnull [attnum]; EEO_NEXT ();} EEO_CASE (EEOP_ASSIGN_TMP) {int resultnum = op- > d. Assignmenttmp.resultnum; resultslot- > tts_ values [resultnum] = state- > resvalue Resultslot- > tts_ isnull [resultnum] = state- > resnull; EEO_NEXT ();} EEO_CASE (EEOP_ASSIGN_TMP_MAKE_RO) {int resultnum = op- > d.signaccountmp.resultnum; resultslot- > tts_ isnull [resultnum] = state- > resnull If (! resultslot- > tts_ isnull [resultnum]) resultslot- > tts_ values [resultnum] = MakeExpandedObjectReadOnlyInternal (state- > resvalue); else resultslot- > tts_ values [resultnum] = state- > resvalue; EEO_NEXT ();} EEO_CASE (EEOP_CONST) {* op- > resnull = op- > d.constval.isnull * op- > resvalue = op- > d.val.value; EEO_NEXT ();} / * * Function-call implementations. Arguments have previously been * evaluated directly into fcinfo- > args. * * As both STRICT checks and function-usage are noticeable performance * wise, and function calls are a very hot-path (they also back * operators!), it's worth having so many separate opcodes. * * Note: the reason for using a temporary variable "d", here and in * other places, is that some compilers think "* op- > resvalue = f (); * requires them to evaluate op- > resvalue into a register before * calling f (), just in case f () is able to modify op- > resvalue * somehow. The extra line of code can save a useless register spill * and reload across the function call. * / EEO_CASE (EEOP_FUNCEXPR) {FunctionCallInfo fcinfo = op- > d.func.fcinfodata; Datum d; fcinfo- > isnull = false; d = op- > d.func.fn_addr (fcinfo); * op- > resvalue = d; * op- > resnull = fcinfo- > isnull; EEO_NEXT () } EEO_CASE (EEOP_FUNCEXPR_STRICT) {FunctionCallInfo fcinfo = op- > d.func.fcinfodata; bool * argnull = fcinfo- > argnull; int argno; Datum d; / * strict function, so check for NULL args * / for (argno = 0; argno

< op->

< 0); break; case ROWCOMPARE_LE: *op->

< nargs; argno++) { if (nulls[argno]) EEO_JUMP(op->

< 3; 调用栈 (gdb) bt#0 ExecInterpExpr (state=0x1e6baa8, econtext=0x1e6b6d8, isnull=0x7fffdbc3b877) at execExprInterp.c:402#1 0x00000000006cd7ed in ExecInterpExprStillValid (state=0x1e6baa8, econtext=0x1e6b6d8, isNull=0x7fffdbc3b877) at execExprInterp.c:1786#2 0x00000000006e1f7f in ExecEvalExprSwitchContext (state=0x1e6baa8, econtext=0x1e6b6d8, isNull=0x7fffdbc3b877) at ../../../src/include/executor/executor.h:313#3 0x00000000006e1fe8 in ExecProject (projInfo=0x1e6baa0) at ../../../src/include/executor/executor.h:347#4 0x00000000006e2358 in ExecScan (node=0x1e6b5c0, accessMtd=0x7103a9 , recheckMtd=0x710474 ) at execScan.c:201#5 0x00000000007104be in ExecSeqScan (pstate=0x1e6b5c0) at nodeSeqscan.c:129#6 0x00000000006e05bb in ExecProcNodeFirst (node=0x1e6b5c0) at execProcnode.c:445#7 0x00000000006d551e in ExecProcNode (node=0x1e6b5c0) at ../../../src/include/executor/executor.h:247#8 0x00000000006d7d56 in ExecutePlan (estate=0x1e6b3a8, planstate=0x1e6b5c0, use_parallel_mode=false, operation=CMD_SELECT, sendTuples=true, numberTuples=0, direction=ForwardScanDirection, dest=0x1e5ff50, execute_once=true) at execMain.c:1723#9 0x00000000006d5ae8 in standard_ExecutorRun (queryDesc=0x1da77e8, direction=ForwardScanDirection, count=0, execute_once=true) at execMain.c:364#10 0x00000000006d5910 in ExecutorRun (queryDesc=0x1da77e8, direction=ForwardScanDirection, count=0, execute_once=true) at execMain.c:307#11 0x00000000008c2206 in PortalRunSelect (portal=0x1df4608, forward=true, count=0, dest=0x1e5ff50) at pquery.c:932#12 0x00000000008c1ea4 in PortalRun (portal=0x1df4608, count=9223372036854775807, isTopLevel=true, run_once=true, dest=0x1e5ff50, altdest=0x1e5ff50, completionTag=0x7fffdbc3bc20 "") at pquery.c:773#13 0x00000000008bbf06 in exec_simple_query (query_string=0x1d85d78 "select 1+id from t_expr;") at postgres.c:1145#14 0x00000000008c0191 in PostgresMain (argc=1, argv=0x1db3cd8, dbname=0x1db3b40 "testdb", username=0x1db3b20 "xdb") at postgres.c:4182#15 0x000000000081e06c in BackendRun (port=0x1da7ae0) at postmaster.c:4361#16 0x000000000081d7df in BackendStartup (port=0x1da7ae0) at postmaster.c:4033#17 0x0000000000819bd9 in ServerLoop () at postmaster.c:1706---Type to continue, or q to quit---#18 0x000000000081948f in PostmasterMain (argc=1, argv=0x1d80a50) at postmaster.c:1379#19 0x0000000000742931 in main (argc=1, argv=0x1d80a50) at main.c:228 跟踪分析 进入ExecInterpExpr Breakpoint 1, ExecInterpExpr (state=0x1e67678, econtext=0x1e672a8, isnull=0x7fffdbc3b897) at execExprInterp.c:402402 if (unlikely(state == NULL))(gdb) cContinuing.Breakpoint 1, ExecInterpExpr (state=0x1e67678, econtext=0x1e672a8, isnull=0x7fffdbc3b877) at execExprInterp.c:402402 if (unlikely(state == NULL)) 获取步骤数组和相关的slot (gdb) n409 op = state->

Steps; (gdb) 410 resultslot = state- > resultslot; (gdb) 411 innerslot = econtext- > ecxt_innertuple; (gdb) 412 outerslot = econtext- > ecxt_outertuple (gdb) p * econtext$21 = {type = T_ExprContext, ecxt_scantuple = 0x1e673a0, ecxt_innertuple = 0x0, ecxt_outertuple = 0x0, ecxt_per_query_memory = 0x1e66e60, ecxt_per_tuple_memory = 0x1e6d290, ecxt_param_exec_vals = 0x0, ecxt_param_list_info = 0x0, ecxt_aggvalues = 0x0, ecxt_aggnulls = 0x0, caseValue_datum = 0, caseValue_isNull = true, domainValue_datum = 0, domainValue_isNull = true, ecxt_estate = 0x1e66f78 Ecxt_callbacks = 0x0} (gdb) n413 scanslot = econtext- > ecxt_scantuple (gdb) (gdb) p * scanslot$22 = {type = T_TupleTableSlot, tts_isempty = false, tts_shouldFree = false, tts_shouldFreeMin = false, tts_slow = false, tts_tuple = 0x1e683f0, tts_tupleDescriptor = 0x7fa4f307fab8, tts_mcxt = 0x1e66e60, tts_buffer = 98, tts_nvalid = 0, tts_values = 0x1e67400, tts_isnull = 0x1e67408, tts_mintuple = 0x0, tts_minhdr = {t_len = 0, t_self = {ip_blkid = {bi_hi = 0, bi_lo = 0} Ip_posid = 0}, t_tableOid = 0, t_data = 0x0}, tts_off = 0, tts_fixedTupleDescriptor = true}

Carry out distribution

416 EEO_DISPATCH ()

First, EEOP_SCAN_FETCHSOME (STEP 1) to get the result slot

(gdb) n443 slot_getsomeattrs (scanslot, op- > d.fetch.last_var); (gdb) n445 EEO_NEXT (); (gdb)

Jump to the next step EEOP_SCAN_VAR (STEP 2) to get the id column values obtained by scanning

480 int attnum = op- > d.var.attnum; (gdb) 484 Assert (attnum > = 0 & & attnum

< scanslot->

Tts_nvalid); (gdb) 485 * op- > resvalue = scanslot- > tts_values [attnum]; (gdb) 486 * op- > resnull = scanslot- > tts_isnull [attnum]; (gdb) 488 EEO_NEXT (); (gdb)

Jump to the next step EEOP_FUNCEXPR_STRICT (STEP 3)

First, the function call information (parameters) is obtained, and then the loop judgment is made according to the number of parameters. Then the actual function (the function pointed to by fn_addr) is called, and the value is assigned to the union d.

663 FunctionCallInfo fcinfo = op- > d.func.fcinfodata; (gdb) 664 bool * argnull = fcinfo- > argnull (gdb) p fcinfo$23 = (FunctionCallInfo) 0x1e67b78 (gdb) p * fcinfo$24 = {flinfo = 0x1e67b20, context = 0x0, resultinfo = 0x0, fncollation = 0, isnull = false, nargs = 2, arg = {1,1,0}, argnull = {false}} (gdb) p * fcinfo- > flinfo$25 = {fn_addr = 0x93d60c, fn_oid = 177, fn_nargs = 2, fn_strict = true, fn_retset = false, fn_stats = 2'\ 002, fn_extra = 0x0, fn_mcxt = 0x1e66e60 Fn_expr = 0x1d87bf8} (gdb) p * fcinfo- > flinfo- > fn_expr$26 = {type = T_OpExpr} (gdb) n669 for (argno = 0 Argno

< op->

D.func.narks; argno++) (gdb) 671 if (Argnall [argno]) (gdb) 669 for (argno = 0; argno)

< op->

D.func.narks; argno++) (gdb) 671 if (Argnall [argno]) (gdb) 669 for (argno = 0; argno)

< op->

D. Func.narks; argno++) (gdb) 677 fcinfo- > isnull = false; (gdb) 678 d = op- > d.func.fn_addr (fcinfo); (gdb) 679 * op- > resvalue = d; (gdb) 680 * op- > resnull = fcinfo- > isnull; (gdb) 683 EEO_NEXT (); (gdb)

Jump to the next step EEOP_ASSIGN_TMP (STEP 4), get the number of the result column, and assign a value

(gdb) 605 resultslot- > tts_ values [resultnum] = state- > resvalue; (gdb) 606 resultslot- > tts_ isnull [resultnum] = state- > resnull; (gdb) p state- > resvalue$27 = 2 (gdb) n608 EEO_NEXT ()

Jump to the next step, EEO_DONE (STEP 5)

(gdb) 423 goto out

Exit and return the result value

(gdb) n1764 * isnull = state- > resnull; (gdb) 1765 return state- > resvalue; (gdb) 1766} (gdb) ExecInterpExprStillValid (state=0x1e67678, econtext=0x1e672a8, isNull=0x7fffdbc3b877) at execExprInterp.c:17871787} (gdb) cContinuing. The above is all the content of the article "how PostgreSQL parses the expression column in the query statement and calculates the value of that column". Thank you for reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.