I read it many times but I'am not entirely familiar with concepts of range table and I'am not sure to fully understant all implications.
For now I have a workaround by parsing only plan's target list and by checking if resorigtbl is equal to oid of my table. The main drawback is that I can't detect column if it is used in a function or an aggregator.
Mathieu PUJOL wrote: > I understand that I should also use varno to check which table is referenced by varattno. In case of Join, aggregation, etc. Sometimes I get a number or INNER_VAR or OUTER_VAR. > I am lost on how i could resolve this. > I understand that OUTER_VAR/INNER_VAR are related to joins sub plans. Is outer related to left plan and inner to right plan ? In this case varattno is index of target list of subplan ? > When varno is an index how to retrieve table info ?
I have no deep understanding of these things.
Maybe the following comment from include/nodes/primnodes.h can help:
/* * Var - expression node representing a variable (ie, a table column) * * Note: during parsing/planning, varnoold/varoattno are always just copies * of varno/varattno. At the tail end of planning, Var nodes appearing in * upper-level plan nodes are reassigned to point to the outputs of their * subplans; for example, in a join node varno becomes INNER_VAR or OUTER_VAR * and varattno becomes the index of the proper element of that subplan's * target list. Similarly, INDEX_VAR is used to identify Vars that reference * an index column rather than a heap column. (In ForeignScan and CustomScan * plan nodes, INDEX_VAR is abused to signify references to columns of a * custom scan tuple type.) In all these cases, varnoold/varoattno hold the * original values. The code doesn't really need varnoold/varoattno, but they * are very useful for debugging and interpreting completed plans, so we keep * them around. */ #define INNER_VAR 65000 /* reference to inner subplan */ #define OUTER_VAR 65001 /* reference to outer subplan */ #define INDEX_VAR 65002 /* reference to index column */