diff options
Diffstat (limited to 'src/include/nodes/relation.h')
| -rw-r--r-- | src/include/nodes/relation.h | 41 |
1 files changed, 28 insertions, 13 deletions
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h index b611e0b905a..a2853fbf044 100644 --- a/src/include/nodes/relation.h +++ b/src/include/nodes/relation.h @@ -339,6 +339,7 @@ typedef struct PlannerInfo * Vars and PlaceHolderVars) * lateral_relids - required outer rels for LATERAL, as a Relids set * (for child rels this can be more than lateral_vars) + * lateral_referencers - relids of rels that reference this one laterally * indexlist - list of IndexOptInfo nodes for relation's indexes * (always NIL if it's not a table) * pages - number of disk pages in relation (zero if not a table) @@ -432,6 +433,7 @@ typedef struct RelOptInfo int32 *attr_widths; /* array indexed [min_attr .. max_attr] */ List *lateral_vars; /* LATERAL Vars and PHVs referenced by rel */ Relids lateral_relids; /* minimum parameterization of rel */ + Relids lateral_referencers; /* rels that reference me laterally */ List *indexlist; /* list of IndexOptInfo */ BlockNumber pages; /* size estimates derived from pg_class */ double tuples; @@ -1344,30 +1346,38 @@ typedef struct SpecialJoinInfo /* * "Lateral join" info. * - * Lateral references in subqueries constrain the join order in a way that's - * somewhat like outer joins, though different in detail. We construct one or - * more LateralJoinInfos for each RTE with lateral references, and add them to - * the PlannerInfo node's lateral_info_list. + * Lateral references constrain the join order in a way that's somewhat like + * outer joins, though different in detail. We construct a LateralJoinInfo + * for each lateral cross-reference, placing them in the PlannerInfo node's + * lateral_info_list. * - * lateral_rhs is the relid of a baserel with lateral references, and - * lateral_lhs is a set of relids of baserels it references, all of which - * must be present on the LHS to compute a parameter needed by the RHS. - * Typically, lateral_lhs is a singleton, but it can include multiple rels - * if the RHS references a PlaceHolderVar with a multi-rel ph_eval_at level. - * We disallow joining to only part of the LHS in such cases, since that would - * result in a join tree with no convenient place to compute the PHV. + * For unflattened LATERAL RTEs, we generate LateralJoinInfo(s) in which + * lateral_rhs is the relid of the LATERAL baserel, and lateral_lhs is a set + * of relids of baserels it references, all of which must be present on the + * LHS to compute a parameter needed by the RHS. Typically, lateral_lhs is + * a singleton, but it can include multiple rels if the RHS references a + * PlaceHolderVar with a multi-rel ph_eval_at level. We disallow joining to + * only part of the LHS in such cases, since that would result in a join tree + * with no convenient place to compute the PHV. * * When an appendrel contains lateral references (eg "LATERAL (SELECT x.col1 * UNION ALL SELECT y.col2)"), the LateralJoinInfos reference the parent * baserel not the member otherrels, since it is the parent relid that is * considered for joining purposes. + * + * If any LATERAL RTEs were flattened into the parent query, it is possible + * that the query now contains PlaceHolderVars containing lateral references, + * representing expressions that need to be evaluated at particular spots in + * the jointree but contain lateral references to Vars from elsewhere. These + * give rise to LateralJoinInfos in which lateral_rhs is the evaluation point + * of a PlaceHolderVar and lateral_lhs is the set of lateral rels it needs. */ typedef struct LateralJoinInfo { NodeTag type; - Index lateral_rhs; /* a baserel containing lateral refs */ - Relids lateral_lhs; /* some base relids it references */ + Relids lateral_lhs; /* rels needed to compute a lateral value */ + Relids lateral_rhs; /* rel where lateral value is needed */ } LateralJoinInfo; /* @@ -1465,6 +1475,10 @@ typedef struct AppendRelInfo * then allow it to bubble up like a Var until the ph_needed join level. * ph_needed has the same definition as attr_needed for a regular Var. * + * The PlaceHolderVar's expression might contain LATERAL references to vars + * coming from outside its syntactic scope. If so, those rels are *not* + * included in ph_eval_at, but they are recorded in ph_lateral. + * * Notice that when ph_eval_at is a join rather than a single baserel, the * PlaceHolderInfo may create constraints on join order: the ph_eval_at join * has to be formed below any outer joins that should null the PlaceHolderVar. @@ -1481,6 +1495,7 @@ typedef struct PlaceHolderInfo Index phid; /* ID for PH (unique within planner run) */ PlaceHolderVar *ph_var; /* copy of PlaceHolderVar tree */ Relids ph_eval_at; /* lowest level we can evaluate value at */ + Relids ph_lateral; /* relids of contained lateral refs, if any */ Relids ph_needed; /* highest level the value is needed at */ int32 ph_width; /* estimated attribute width */ } PlaceHolderInfo; |