Github user DaveBirdsall commented on a diff in the pull request:
https://github.com/apache/incubator-trafodion/pull/750#discussion_r82643315
--- Diff: core/sql/exp/exp_fixup.cpp ---
@@ -1740,6 +1741,103 @@ Lng32
ex_conv_clause::findIndexIntoInstrArray(ConvInstruction ci)
return -1; // not found
}
+bool ex_conv_clause::sv_instrOffsetIndexPopulated = false;
+short ex_conv_clause::sv_MaxOpTypeValue = -1;
+int *ex_conv_clause::sv_convIndexSparse = 0;
+
+/*
+ * Scans convInstrInfo[] and populates a
+ * sparsely populated index: sv_convIndexSparse.
+ *
+ * For a given op type: op_type,
+ * if (sv_convIndexSparse[op_type>] != -1) then
+ * it contains the offset into the first row of
+ * convInstrInfo[]
+ */
+void ex_conv_clause::populateInstrOffsetIndex()
+{
+ if (sv_instrOffsetIndexPopulated) {
+ return;
+ }
+
+ typedef struct convInstrIndexStruct {
+ short type_op1;
+ short offset;
+ } convInstrIndexDef;
+
+ short lv_MaxIndex = -1;
+
+ // Currently, the number of distinct 'type_op1' values in the
convInstrInf[] is 32
+ const int lv_MaxIndexCapacity = 100;
+ convInstrIndexDef lv_convIndex[lv_MaxIndexCapacity];
+
+ Int32 i = 0;
+ Int32 lv_source_type = -1;
+ Int32 lv_max_array_size = sizeof(ex_conv_clause::convInstrInfo) /
sizeof(ex_conv_clause::ConvInstrStruct);
+
+ // collect distinct type_op1 values and their 1st offset in
convInstrInfo[]
+ while (i < lv_max_array_size) {
+ if (ex_conv_clause::convInstrInfo[i].type_op1 != lv_source_type) {
+ lv_source_type = ex_conv_clause::convInstrInfo[i].type_op1;
+ if ((lv_source_type > -1) &&
+ (lv_MaxIndex < (lv_MaxIndexCapacity - 1))) {
+ lv_convIndex[++lv_MaxIndex].type_op1 = lv_source_type;
+ lv_convIndex[lv_MaxIndex].offset = i;
+ }
+ }
+ i++;
+ }
+
+ // Find the max op type value in lv_convIndex
+ int j = 0;
+ while (j <= lv_MaxIndex) {
+ if (sv_MaxOpTypeValue < lv_convIndex[j].type_op1) {
+ sv_MaxOpTypeValue = lv_convIndex[j].type_op1;
+ }
+ j++;
+ }
+
+ // just in case some op type has been assigned a pretty large value
+ // we dont want to allocate a very large sparse value
+ if (sv_MaxOpTypeValue > 8000) {
+ sv_MaxOpTypeValue = 8000;
+ }
+
+ // Allocate a sparsely populated array
+ sv_convIndexSparse = (int *) calloc(sizeof(int),
--- End diff --
I think this logic is idempotent to it probably doesn't matter but it looks
like two threads could do the calloc, one of them will win in setting
sv_convIndexSparse, then both of them could interleave in the initialization
logic below. Could be the fast one sets the sv_instrOffsetIndexPopulated flag
to true while the slow one is in the Initialize to -1 loop so theoretically we
could get wrong answers. Might be safer to use a local variable here and only
set sv_convIndexSparse at the very end just before setting the boolean. Then
the worst thing that happens is we allocated the array twice but it will never
be inconsistent.
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