本节简单介绍了PostgreSQL创建函数的过程，其实现函数是CreateFunction。这里介绍了CreateFunction中的通用函数construct_array。 ### 一、数据结构 **Form_pg_language** plpgsql语言定义结构体 ``` /* ---------------- * pg_language definition. cpp turns this into * typedef struct FormData_pg_language * ---------------- */ CATALOG(pg_language,2612,LanguageRelationId) { Oid oid; /* oid */ /* Language name */ NameData lanname; /* Language's owner */ Oid lanowner BKI_DEFAULT(PGUID); /* Is a procedural language */ bool lanispl BKI_DEFAULT(f); /* PL is trusted */ bool lanpltrusted BKI_DEFAULT(f); /* Call handler, if it's a PL */ Oid lanplcallfoid BKI_DEFAULT(0) BKI_LOOKUP(pg_proc); /* Optional anonymous-block handler function */ Oid laninline BKI_DEFAULT(0) BKI_LOOKUP(pg_proc); /* Optional validation function */ Oid lanvalidator BKI_DEFAULT(0) BKI_LOOKUP(pg_proc); #ifdef CATALOG_VARLEN /* variable-length fields start here */ /* Access privileges */ aclitem lanacl[1] BKI_DEFAULT(_null_); #endif } FormData_pg_language; /* ---------------- * Form_pg_language corresponds to a pointer to a tuple with * the format of pg_language relation. * ---------------- */ typedef FormData_pg_language *Form_pg_language; ``` **ArrayType** ``` /* * Arrays are varlena objects, so must meet the varlena convention that * the first int32 of the object contains the total object size in bytes. * Be sure to use VARSIZE() and SET_VARSIZE() to access it, though! * Arrays是可变对象集，必须符合varlena约定，即对象的第一个int32包含对象的总大小（以字节为单位）。 * 但是，一定要确保使用VARSIZE和SET_VARSIZE函数范围该结构体 * * CAUTION: if you change the header for ordinary arrays you will also * need to change the headers for oidvector and int2vector! */ typedef struct { //可变的header int32 vl_len_; /* varlena header (do not touch directly!) */ //维度 int ndim; /* # of dimensions */ //指向数据的偏移量,如为0则表示没有位图 int32 dataoffset; /* offset to data, or 0 if no bitmap */ //元素类型的OID Oid elemtype; /* element type OID */ } ArrayType; ``` **DefElem** ``` typedef struct DefElem { NodeTag type; char *defnamespace; /* NULL if unqualified name */ char *defname; Node *arg; /* a (Value *) or a (TypeName *) */ DefElemAction defaction; /* unspecified action, or SET/ADD/DROP */ int location; /* token location, or -1 if unknown */ } DefElem; ``` **FunctionParameter** ``` typedef enum FunctionParameterMode { /* the assigned enum values appear in pg_proc, don't change 'em! */ FUNC_PARAM_IN = 'i', /* input only */ FUNC_PARAM_OUT = 'o', /* output only */ FUNC_PARAM_INOUT = 'b', /* both */ FUNC_PARAM_VARIADIC = 'v', /* variadic (always input) */ FUNC_PARAM_TABLE = 't' /* table function output column */ } FunctionParameterMode; typedef struct FunctionParameter { NodeTag type; char *name; /* parameter name, or NULL if not given */ TypeName *argType; /* TypeName for parameter type */ FunctionParameterMode mode; /* IN/OUT/etc */ Node *defexpr; /* raw default expr, or NULL if not given */ } FunctionParameter; ``` ### 二、源码解读 ``` /* *allParameterTypes = construct_array(allTypes, parameterCount, OIDOID,sizeof(Oid), true, 'i'); *parameterModes = construct_array(paramModes, parameterCount, CHAROID,1, true, 'c'); */ /* * construct_array --- simple method for constructing an array object * 构建数组对象的简单方法 * * elems: array of Datum items to become the array contents * (NULL element values are not supported). * nelems: number of items * elmtype, elmlen, elmbyval, elmalign: info for the datatype of the items * * elems: 数组中的元素 * nelems:元素数量 * elmtype,elmlen,elmbyval,elmalign:元素的数据类型信息 * * A palloc'd 1-D array object is constructed and returned. Note that * elem values will be copied into the object even if pass-by-ref type. * Also note the result will be 0-D not 1-D if nelems = 0. * 构建一维数组对象并返回. * 注意元素值即使引用传递类型也会拷贝到对象中. * 同时要注意如元素个数为0,结果是0-D数组而不是一维数组. * * NOTE: it would be cleaner to look up the elmlen/elmbval/elmalign info * from the system catalogs, given the elmtype. However, the caller is * in a better position to cache this info across multiple uses, or even * to hard-wire values if the element type is hard-wired. * 给定elmtype的情况下,从系统目录中获取元素elmlen/elmbval/elmalign应更加清晰. * 但是,调用者便于跨用户缓存这些信息. */ ArrayType * construct_array(Datum *elems, int nelems, Oid elmtype, int elmlen, bool elmbyval, char elmalign) { int dims[1]; int lbs[1]; dims[0] = nelems;//数组元素个数 lbs[0] = 1; return construct_md_array(elems, NULL, 1, dims, lbs, elmtype, elmlen, elmbyval, elmalign); } /* * construct_md_array --- simple method for constructing an array object * with arbitrary dimensions and possible NULLs * construct_md_array:构建任意维度和可能存在NULLs的数据对象 * * elems: array of Datum items to become the array contents * nulls: array of is-null flags (can be NULL if no nulls) * ndims: number of dimensions * dims: integer array with size of each dimension * lbs: integer array with lower bound of each dimension * elmtype, elmlen, elmbyval, elmalign: info for the datatype of the items * elems:同construct_array * nulls:is-null标记数组 * ndims:维度数 * dims:每个维度大小的整型数组 * lbs:每个维度的下界整型数组 * elmtype, elmlen, elmbyval, elmalign: 元素的数据类型信息 * * A palloc'd ndims-D array object is constructed and returned. Note that * elem values will be copied into the object even if pass-by-ref type. * Also note the result will be 0-D not ndims-D if any dims[i] = 0. * 构建ndims维数组并返回. * * NOTE: it would be cleaner to look up the elmlen/elmbval/elmalign info * from the system catalogs, given the elmtype. However, the caller is * in a better position to cache this info across multiple uses, or even * to hard-wire values if the element type is hard-wired. */ ArrayType * construct_md_array(Datum *elems,//元素内容 bool *nulls,//nulls标记数组(每个元素占用一个位置) int ndims,//维度数 int *dims,//每个维度的元素大小 int *lbs,//每个维度的下界数组(low bound) Oid elmtype, int elmlen, bool elmbyval, char elmalign) { ArrayType *result;//结果 bool hasnulls;//是否存在null值 int32 nbytes;//以字节为单位的大小 int32 dataoffset;//数据偏移 int i;//临时变量 int nelems;//元素数目 //校验维数 if (ndims < 0) /* we do allow zero-dimension arrays */ ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE), errmsg("invalid number of dimensions: %d", ndims))); if (ndims > MAXDIM) ereport(ERROR, (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED), errmsg("number of array dimensions (%d) exceeds the maximum allowed (%d)", ndims, MAXDIM))); //元素数目:每个维数的大小相乘 nelems = ArrayGetNItems(ndims, dims); /* if ndims <= 0 or any dims[i] == 0, return empty array */ //维数≤0或者任意一维的个数等于0,返回空数组 if (nelems <= 0) return construct_empty_array(elmtype); /* compute required space */ //计算需要的空间大小 nbytes = 0; hasnulls = false; for (i = 0; i < nelems; i++) { if (nulls && nulls[i]) { //存在null值 hasnulls = true; continue; } /* make sure data is not toasted */ //确保数据没有toasted if (elmlen == -1) elems[i] = PointerGetDatum(PG_DETOAST_DATUM(elems[i])); //以字节为单位的大小 nbytes = att_addlength_datum(nbytes, elmlen, elems[i]); //#define att_align_nominal(cur_offset,attalign) ( ((attalign) == 'i') ? INTALIGN(cur_offset) : (((attalign) == 'c') ? (uintptr_t) (cur_offset) : (((attalign) == 'd') ? DOUBLEALIGN(cur_offset) : ( AssertMacro((attalign) == 's'), SHORTALIGN(cur_offset) ))) ) //( ((elmalign) == 'i') ? (((uintptr_t) ((nbytes)) + ((ALIGNOF_INT) - 1)) & ~((uintptr_t) ((ALIGNOF_INT) - 1))) : (((elmalign) == 'c') ? (uintptr_t) (nbytes) : (((elmalign) == 'd') ? (((uintptr_t) ((nbytes)) + ((ALIGNOF_DOUBLE) - 1)) & ~((uintptr_t) ((ALIGNOF_DOUBLE) - 1))) : ( ((void)((bool) 1)), (((uintptr_t) ((nbytes)) + ((ALIGNOF_SHORT) - 1)) & ~((uintptr_t) ((ALIGNOF_SHORT) - 1))) ))) ) nbytes = att_align_nominal(nbytes, elmalign); /* check for overflow of total request */ //检查是否溢出 //#define AllocSizeIsValid(size) ((Size) (size) <= MaxAllocSize) //((Size) (nbytes) <= ((Size) 0x3fffffff))(2的30次方) if (!AllocSizeIsValid(nbytes)) ereport(ERROR, (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED), errmsg("array size exceeds the maximum allowed (%d)", (int) MaxAllocSize))); } /* Allocate and initialize result array */ //分配和初始化结果数组 if (hasnulls) { //分配null bitmap空间 dataoffset = ARR_OVERHEAD_WITHNULLS(ndims, nelems); nbytes += dataoffset; } else { //无null bitmap dataoffset = 0; /* marker for no null bitmap */ //#define ARR_OVERHEAD_WITHNULLS(ndims,nitems) MAXALIGN(sizeof(ArrayType) + 2 * sizeof(int) * (ndims) + ((nitems) + 7) / 8) //(((uintptr_t) ((sizeof(ArrayType) + 2 * sizeof(int) * (ndims))) + ((MAXIMUM_ALIGNOF) - 1)) & ~((uintptr_t) ((MAXIMUM_ALIGNOF) - 1))) //#define ARR_OVERHEAD_NONULLS(ndims) MAXALIGN(sizeof(ArrayType) + 2 * sizeof(int) * (ndims)) //(((uintptr_t) ((sizeof(ArrayType) + 2 * sizeof(int) * (ndims))) + ((MAXIMUM_ALIGNOF) - 1)) & ~((uintptr_t) ((MAXIMUM_ALIGNOF) - 1))) nbytes += ARR_OVERHEAD_NONULLS(ndims); } //分配空间 result = (ArrayType *) palloc0(nbytes); //设置大小 //SET_VARSIZE --> //#define SET_VARSIZE(PTR,len) SET_VARSIZE_4B(PTR, len) //(((varattrib_4b *) (result))->va_4byte.va_header = (((uint32) (nbytes)) << 2)) //nbytes * 4 SET_VARSIZE(result, nbytes); //维数 result->ndim = ndims; //数据偏移(前面是null bitmap) result->dataoffset = dataoffset; //元素类型 result->elemtype = elmtype; //ARR_DIMS --> 元素个数 //#define ARR_DIMS(a) ((int *) (((char *) (a)) + sizeof(ArrayType))) //((int *) (((char *) (result)) + sizeof(ArrayType))) --> ((int *) (((char *) (result)) + 16)) memcpy(ARR_DIMS(result), dims, ndims * sizeof(int)); //ARR_LBOUND --> 下限边界 //#define ARR_LBOUND(a) ((int *) (((char *) (a)) + sizeof(ArrayType) + sizeof(int) * ARR_NDIM(a))) //((int *) (((char *) (result)) + sizeof(ArrayType) + sizeof(int) * ((result)->ndim))) memcpy(ARR_LBOUND(result), lbs, ndims * sizeof(int)); //拷贝数组元素 CopyArrayEls(result, elems, nulls, nelems, elmlen, elmbyval, elmalign, false); return result; } /* * Convert array dimensions into number of elements * 转换数组的维数为元素个数 * * This must do overflow checking, since it is used to validate that a user * dimensionality request doesn't overflow what we can handle. * 必须执行溢出检查. * * We limit array sizes to at most about a quarter billion elements, * so that it's not necessary to check for overflow in quite so many * places --- for instance when palloc'ing Datum arrays. * 数组的大小限制在大概100w/4. * * The multiplication overflow check only works on machines that have int64 * arithmetic, but that is nearly all platforms these days, and doing check * divides for those that don't seems way too expensive. */ int ArrayGetNItems(int ndim, const int *dims) { int32 ret; int i; #define MaxArraySize ((Size) (MaxAllocSize / sizeof(Datum))) if (ndim <= 0) return 0; ret = 1; for (i = 0; i < ndim; i++) { int64 prod; /* A negative dimension implies that UB-LB overflowed ... */ if (dims[i] < 0) ereport(ERROR, (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED), errmsg("array size exceeds the maximum allowed (%d)", (int) MaxArraySize))); prod = (int64) ret * (int64) dims[i]; ret = (int32) prod; if ((int64) ret != prod) ereport(ERROR, (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED), errmsg("array size exceeds the maximum allowed (%d)", (int) MaxArraySize))); } Assert(ret >= 0); if ((Size) ret > MaxArraySize) ereport(ERROR, (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED), errmsg("array size exceeds the maximum allowed (%d)", (int) MaxArraySize))); return (int) ret; } /* * Copy data into an array object from a temporary array of Datums. * 从Datums临时数组中拷贝数据到数组对象中. * * array: array object (with header fields already filled in) * values: array of Datums to be copied * nulls: array of is-null flags (can be NULL if no nulls) * nitems: number of Datums to be copied * typbyval, typlen, typalign: info about element datatype * freedata: if true and element type is pass-by-ref, pfree data values * referenced by Datums after copying them. * * array:数组对象(头部已填充) * values:将要拷贝的Datums数组 * nulls:is-null标记数组 * nitems:元素数目 * typbyval,typlen, typalign:元素数据类型信息 * freedata:如为T并且元素类型是引用传递,则拷贝后释放空间 * * If the input data is of varlena type, the caller must have ensured that * the values are not toasted. (Doing it here doesn't work since the * caller has already allocated space for the array...) * 如果输入数据是varlena类型,调用者必须确保值没有toasted. */ void CopyArrayEls(ArrayType *array, Datum *values, bool *nulls, int nitems, int typlen, bool typbyval, char typalign, bool freedata) { //#define ARR_DATA_PTR(a) (((char *) (a)) + ARR_DATA_OFFSET(a)) //(((char *) (array)) + (((array)->dataoffset != 0) ? (array)->dataoffset : (((uintptr_t) ((sizeof(ArrayType) + 2 * sizeof(int) * (((array)->ndim)))) + ((MAXIMUM_ALIGNOF) - 1)) & ~((uintptr_t) ((MAXIMUM_ALIGNOF) - 1))))) char *p = ARR_DATA_PTR(array); //#define ARR_NULLBITMAP(a) (ARR_HASNULL(a) ? (bits8 *) (((char *) (a)) + sizeof(ArrayType) + 2 * sizeof(int) * ARR_NDIM(a)) : (bits8 *) NULL) //(((array)->dataoffset != 0) ? (bits8 *) (((char *) (array)) + sizeof(ArrayType) + 2 * sizeof(int) * ((array)->ndim)) : (bits8 *) NULL) bits8 *bitmap = ARR_NULLBITMAP(array); int bitval = 0; int bitmask = 1; int i; if (typbyval)//传值 freedata = false; for (i = 0; i < nitems; i++)//遍历元素 { if (nulls && nulls[i]) { //如为null,则bitmap不能为空指针 if (!bitmap) /* shouldn't happen */ elog(ERROR, "null array element where not supported"); /* bitmap bit stays 0 */ } else { // bitval |= bitmask; p += ArrayCastAndSet(values[i], typlen, typbyval, typalign, p); if (freedata) pfree(DatumGetPointer(values[i])); } if (bitmap) { bitmask <<= 1; if (bitmask == 0x100) { *bitmap++ = bitval; bitval = 0; bitmask = 1; } } } if (bitmap && bitmask != 1) *bitmap = bitval; } /* * Copy datum to *dest and return total space used (including align padding) * * Caller must have handled case of NULL element */ static int ArrayCastAndSet(Datum src, int typlen, bool typbyval, char typalign, char *dest) { int inc; if (typlen > 0) { if (typbyval) store_att_byval(dest, src, typlen); else memmove(dest, DatumGetPointer(src), typlen); inc = att_align_nominal(typlen, typalign); } else { Assert(!typbyval); inc = att_addlength_datum(0, typlen, src); memmove(dest, DatumGetPointer(src), inc); inc = att_align_nominal(inc, typalign); } return inc; } ``` ### 三、跟踪分析 测试脚本 ``` create or replace function func_test(pi_v1 in int,pi_v2 varchar,pio_v3 inout varchar,po_v4 out int,po_v5 out varchar) returns record as $$ declare begin raise notice 'pi_v1 := %,pi_v2 := %,pi_v3 := %',pi_v1,pi_v2,pio_v3; pio_v3 := 'pio_v3 i/o'; po_v4 := 100; po_v5 := 'po_v5 out'; end; $$ LANGUAGE plpgsql; ``` 启动GDB跟踪 ``` (gdb) b construct_array Breakpoint 1 at 0x91eaeb: file arrayfuncs.c, line 3298. (gdb) c Continuing. Breakpoint 1, construct_array (elems=0x22d9da0, nelems=5, elmtype=26, elmlen=4, elmbyval=true, elmalign=105 'i') at arrayfuncs.c:3298 3298 dims[0] = nelems; (gdb) bt #0 construct_array (elems=0x22d9da0, nelems=5, elmtype=26, elmlen=4, elmbyval=true, elmalign=105 'i') at arrayfuncs.c:3298 #1 0x000000000066fa48 in interpret_function_parameter_list (pstate=0x22d9c88, parameters=0x22b3d30, languageOid=13581, objtype=OBJECT_FUNCTION, parameterTypes=0x7fff6bde92b8, allParameterTypes=0x7fff6bde92b0, parameterModes=0x7fff6bde92a8, parameterNames=0x7fff6bde92a0, parameterDefaults=0x7fff6bde9298, variadicArgType=0x7fff6bde9294, requiredResultType=0x7fff6bde9290) at functioncmds.c:434 #2 0x000000000067100f in CreateFunction (pstate=0x22d9c88, stmt=0x22b48c8) at functioncmds.c:1053 #3 0x00000000008f61a6 in ProcessUtilitySlow (pstate=0x22d9c88, pstmt=0x22b4c48, queryString=0x22b2ed8 "create or replace function func_test(pi_v1 in int,pi_v2 varchar,pio_v3 inout varchar,po_v4 out int,po_v5 out varchar)\nreturns record \nas\n$$\ndeclare\nbegin\n raise notice 'pi_v1 := %,pi_v2 := %,pi_v3 :="..., context=PROCESS_UTILITY_TOPLEVEL, params=0x0, queryEnv=0x0, dest=0x22b4d40, completionTag=0x7fff6bde9a60 "") at utility.c:1478 #4 0x00000000008f5069 in standard_ProcessUtility (pstmt=0x22b4c48, queryString=0x22b2ed8 "create or replace function func_test(pi_v1 in int,pi_v2 varchar,pio_v3 inout varchar,po_v4 out int,po_v5 out varchar)\nreturns record \nas\n$$\ndeclare\nbegin\n raise notice 'pi_v1 := %,pi_v2 := %,pi_v3 :="..., context=PROCESS_UTILITY_TOPLEVEL, params=0x0, queryEnv=0x0, dest=0x22b4d40, completionTag=0x7fff6bde9a60 "") at utility.c:927 #5 0x00000000008f418f in ProcessUtility (pstmt=0x22b4c48, queryString=0x22b2ed8 "create or replace function func_test(pi_v1 in int,pi_v2 varchar,pio_v3 inout varchar,po_v4 out int,po_v5 out varchar)\nreturns record \nas\n$$\ndeclare\nbegin\n raise notice 'pi_v1 := %,pi_v2 := %,pi_v3 :="..., context=PROCESS_UTILITY_TOPLEVEL, params=0x0, queryEnv=0x0, dest=0x22b4d40, completionTag=0x7fff6bde9a60 "") at utility.c:360 #6 0x00000000008f3188 in PortalRunUtility (portal=0x231a248, pstmt=0x22b4c48, isTopLevel=true, setHoldSnapshot=false, dest=0x22b4d40, completionTag=0x7fff6bde9a60 "") at pquery.c:1175 #7 0x00000000008f339e in PortalRunMulti (portal=0x231a248, isTopLevel=true, setHoldSnapshot=false, dest=0x22b4d40, altdest=0x22b4d40, completionTag=0x7fff6bde9a60 "") at pquery.c:1321 #8 0x00000000008f28d3 in PortalRun (portal=0x231a248, count=9223372036854775807, isTopLevel=true, run_once=true, dest=0x22b4d40, altdest=0x22b4d40, completionTag=0x7fff6bde9a60 "") at pquery.c:796 #9 0x00000000008ec882 in exec_simple_query ( query_string=0x22b2ed8 "create or replace function func_test(pi_v1 in int,pi_v2 varchar,pio_v3 inout varchar,po_v4 out int,po_v5 out varchar)\nreturns record \nas\n$$\ndeclare\nbegin\n ---Type <return> to continue, or q <return> to quit---^CQuit (gdb) ``` 输入参数: 5个参数的OID,分别是23/1043/1043/23/1043;有5个元素;类型为26-OID;元素长度为4(int32);以传值方式传递;对其方式为i-INT ``` (gdb) p elems[0] $73 = 23 (gdb) p elems[1] $74 = 1043 (gdb) p elems[2] $75 = 1043 (gdb) p elems[3] $76 = 23 (gdb) p elems[4] $77 = 1043 (gdb) ``` 进入construct_md_array,输入参数维数-1,5个元素,数组下界为1 ``` (gdb) n 3299 lbs[0] = 1; (gdb) 3301 return construct_md_array(elems, NULL, 1, dims, lbs, (gdb) step construct_md_array (elems=0x22d9dd8, nulls=0x0, ndims=1, dims=0x7fff6bde9070, lbs=0x7fff6bde9060, elmtype=26, elmlen=4, elmbyval=true, elmalign=105 'i') at arrayfuncs.c:3340 3340 if (ndims < 0) /* we do allow zero-dimension arrays */ (gdb) ``` 执行相关校验(最大维数为6),获取元素个数(5) ``` (gdb) n 3344 if (ndims > MAXDIM) (gdb) p MAXDIM $78 = 6 (gdb) n 3350 nelems = ArrayGetNItems(ndims, dims); (gdb) 3353 if (nelems <= 0) (gdb) p nelems $79 = 5 (gdb) ``` 计算需占用的空间 ``` (gdb) n 3357 nbytes = 0; (gdb) 3358 hasnulls = false; (gdb) 3359 for (i = 0; i < nelems; i++) (gdb) 3361 if (nulls && nulls[i]) (gdb) 3367 if (elmlen == -1) (gdb) 3369 nbytes = att_addlength_datum(nbytes, elmlen, elems[i]); (gdb) 3370 nbytes = att_align_nominal(nbytes, elmalign); (gdb) 3372 if (!AllocSizeIsValid(nbytes)) (gdb) 3359 for (i = 0; i < nelems; i++) (gdb) 3361 if (nulls && nulls[i]) (gdb) 3367 if (elmlen == -1) (gdb) 3369 nbytes = att_addlength_datum(nbytes, elmlen, elems[i]); (gdb) 3370 nbytes = att_align_nominal(nbytes, elmalign); (gdb) 3372 if (!AllocSizeIsValid(nbytes)) (gdb) 3359 for (i = 0; i < nelems; i++) (gdb) 3361 if (nulls && nulls[i]) (gdb) 3367 if (elmlen == -1) (gdb) 3369 nbytes = att_addlength_datum(nbytes, elmlen, elems[i]); (gdb) 3370 nbytes = att_align_nominal(nbytes, elmalign); (gdb) 3372 if (!AllocSizeIsValid(nbytes)) (gdb) 3359 for (i = 0; i < nelems; i++) (gdb) 3361 if (nulls && nulls[i]) (gdb) 3367 if (elmlen == -1) (gdb) 3369 nbytes = att_addlength_datum(nbytes, elmlen, elems[i]); (gdb) 3370 nbytes = att_align_nominal(nbytes, elmalign); (gdb) 3372 if (!AllocSizeIsValid(nbytes)) (gdb) 3359 for (i = 0; i < nelems; i++) (gdb) 3361 if (nulls && nulls[i]) (gdb) 3367 if (elmlen == -1) (gdb) 3369 nbytes = att_addlength_datum(nbytes, elmlen, elems[i]); (gdb) 3370 nbytes = att_align_nominal(nbytes, elmalign); (gdb) 3372 if (!AllocSizeIsValid(nbytes)) (gdb) 3359 for (i = 0; i < nelems; i++) (gdb) 3380 if (hasnulls) (gdb) ``` 5个OID,需占用20个bytes ``` (gdb) p nbytes $80 = 20 (gdb) ``` 没有null bitmap,偏移为0;添加头部空间(ArrayType的大小16+2\*4\*维数,这里是24) ``` (gdb) n 3387 dataoffset = 0; /* marker for no null bitmap */ (gdb) 3388 nbytes += ARR_OVERHEAD_NONULLS(ndims); (gdb) 3390 result = (ArrayType *) palloc0(nbytes); (gdb) p nbyes $81 = 44 (gdb) ``` 分配空间,赋值结构体 ``` (gdb) n 3391 SET_VARSIZE(result, nbytes); (gdb) n 3392 result->ndim = ndims; (gdb) p nbytes $82 = 44 (gdb) p *result $83 = {vl_len_ = 176, ndim = 0, dataoffset = 0, elemtype = 0} (gdb) n 3393 result->dataoffset = dataoffset; (gdb) 3394 result->elemtype = elmtype; (gdb) 3395 memcpy(ARR_DIMS(result), dims, ndims * sizeof(int));-->元素个数 (gdb) 3396 memcpy(ARR_LBOUND(result), lbs, ndims * sizeof(int));-->第一个维度的下界 (gdb) p *result $84 = {vl_len_ = 176, ndim = 1, dataoffset = 0, elemtype = 26} (gdb) p *(int *)((char *)result+16) $85 = 5 (gdb) p *(int *)((char *)result+20) $86 = 0 (gdb) p *(int *)((char *)result+24) $87 = 0 (gdb) p *(int *)((char *)result+28) $88 = 0 (gdb) n 3398 CopyArrayEls(result, (gdb) p *(int *)((char *)result+20) $89 = 1 (gdb) ``` 拷贝OID到数组中,从24开始,每个值占用4个byte,共5个值 ``` (gdb) n 3403 return result; (gdb) p *(int *)((char *)result+24) $90 = 23 (gdb) p *(int *)((char *)result+28) $91 = 1043 (gdb) p *(int *)((char *)result+32) $92 = 1043 (gdb) p *(int *)((char *)result+36) $93 = 23 (gdb) p *(int *)((char *)result+40) $94 = 1043 (gdb) ``` 完成函数调用 ``` (gdb) n 3404 } (gdb) construct_array (elems=0x22d9dd8, nelems=5, elmtype=26, elmlen=4, elmbyval=true, elmalign=105 'i') at arrayfuncs.c:3303 3303 } (gdb) ``` DONE! ### 四、参考资料 N/A